Hotel room numbering

CJam, 34 31 bytes

qN/W%zSf-La%{_{s'*&}#_)@@=}3*;\

This requires the input to be padded to a rectangle with spaces.

Try it online! Alternatively, run all test cases.

Explanation

qN/      e# Read input and split into lines.
W%z      e# Rotate 90° counter-clockwise.
Sf-      e# Remove all spaces from the rows.
La%      e# Split into buildings. We've now got a 3D array of rooms, where the first
         e# dimension is the building, the second the room number and the third is the
         e# the floor number.
{        e# Run this block three times. At each stage it will find the index of the "*"
         e# along the current dimension and leave the element at that index on the stack
         e# for the next round...
  _      e#   Duplicate the current array.
  {      e#   Find the index of the first element where this block yields something
         e#   truthy...
    s    e#     Flatten into a single string.
    '*&  e#     Set intersection with "*".
  }#
  _)     e#   Duplicate the index and increment it, because the results should be 1-based.
  @@=    e#   Pull up the array and the other copy of the index and select the
         e#   corresponding element.
}3*
;\       e# We've now got the building, room and floor index on the stack, as well as the
         e# "*" character itself. We discard the character and swap the room and the floor
         e# floor number. When the three indices are printed back-to-back at the end of
         e# the program, that will yield the desired result.

JavaScript (ES6), 142 136 bytes

h=>h.split`
`.reverse(r=0).map((t,i,l)=>r?0:(f=i+1,b=1,l[o=0].slice(0,r=t.indexOf`*`+1).replace(/  /g,(_,s)=>o=++b&&s+2),r-=o))&&[b]+f+r

6 bytes saved thanks to @nderscore!

Explanation

h=>
  h.split`
`                            // get each line of the input string
  .reverse(                  // reverse the lines to make getting the ground floor easy
    r=0)                     // initialise r to 0
  .map((t,i,l)=>             // for each line of the reversed input string
    r?0:(                    // if the marked room has not been found yet:
      f=i+1,                 // f = floor number
      b=1,                   // b = building number, default to 1
      l[o=0].slice(0,        // get the substring of 0 to the marked room, default o to 0
        r=t.indexOf`*`+1)    // r = absolute index of room + 1 (or 0 if not found)
      .replace(/  /g,(_,s)=> // count the spaces between buildings
        o=++b&&s+2),         // increment b, o = index of marked room's building
      r-=o                   // make r relative to the room's building
    )
  )
  &&[b]+f+r                  // output the result ([b] casts b to a string)

Test

var solution = h=>h.split`
`.reverse(r=0).map((t,i,l)=>r?0:(f=i+1,b=1,l[o=0].slice(0,r=t.indexOf`*`+1).replace(/  /g,(_,s)=>o=++b&&s+2),r-=o))&&[b]+f+r
<textarea id="input" rows="8" cols="60">#
#  #
#  #  ##
#  #  ##  ###
#  #  ##  ###  #####
#  #  ##  ###  ##*##  ########
#  #  ##  ###  #####  ########</textarea><br />
<button onclick="result.textContent=solution(input.value)">Go</button>
<pre id="result"></pre>


Pyth, 34 bytes

LxKh/#\*b\*jkhM[//<hJ_.zyJd2xJKycK

Demonstration

This uses a golfing trick I've never used before: Assigning to a variable (K) inside a function (y) to save a partial result from that function.

Explanation:

LxKh/#\*b\*jkhM[//<hJ_.zyJd2xJKycK
L                                     Define y(b):      (b is a list of strigs)
    /#\*b                             Filter b for strings containing '*'
   h                                  Take the first such string
  K                                   Store it in K
 x       \*                           And return the index of '*' in that string.
                      .z              Take the input as a list of strings
                     _                Reverse it (bottom to top)
                    J                 Store in J
                   h                  Take the bottommost row
                        yJ            Find y(J). This is the index in whichever
                                      row of J has the * of the *. Also store
                                      that row in K.
                  <                   Slice J up to that index.
                 /        d           Count the number of spaces
                /          2          Divide by 2. This is the building number.
                            xJK       Take the index in J of K. This is the floor.
                                cK    Chop K on whitespace.
                               y      Find the index in whatever element of K has
                                      the * of the *. This is the room number.
                                      This also overwrites K, but we don't care.
               [                      Gather the above into a list.
             hM                       Convert 0-indexing to 1-indexing.
           jk                         Concatenate. Print implicitly.