plz send teh codez!

JavaScript (ES6), 60 bytes

x=>/Plz send teh codez!/.test(x)?~x+' flag comment':'+'+-~[]

Everything was straightforward, except avoiding using 1 anywhere. I use ~x to get -1 (since if x contains Plz send teh codez!, it's not a valid number and therefore ~x will give -1), and -~[] to get 1 (since if x is e.g. '7', -~x will be 8, so we can't rely on x).

Test snippet

let f =
x=>/Plz send teh codez!/.test(x)?~x+' flag comment':'+'+-~[];

console.log(f("Hello, Plz send teh codez!"))
console.log(f("Hello, Plz send teh codez?"))

JS (JSFuck), 37959 bytes

Here's a gist, since PPCG hates long codes.

Only uses special characters. :P

Heres the original code:

alert(prompt().includes("Plz send teh codez!")?"-1 flag comment":"+1")

C, 102 bytes

i;f(char*s){i=strstr(s,"Plz send teh codez!");printf("%+d%s",i?'a'-'b':'b'-'a',i?" flag comment":"");}

Doesn't use any digit or any of QWERTYUIOASDFGHJKLXVBN. Try it online!