Perforce File Locked By Departed User

"Locked" and "checked out" are two different things which require two different operations to undo. As Peter G. said, an admin can unlock a file with the unlock command:

p4 unlock -f <file>

However, to revert a file checked out by another user, you need to impersonate that user by passing their client (workspace name), host (computer name) and user names to the revert command, like so:

p4 -c theirclient -H theirhost -u theiruser revert filename

So if a Perforce user named jdoe has file foo.txt checked out in workspace ws1 on a host named joesPC, an admin can revert it with the following command:

p4 -c ws1 -H joesPC -u jdoe revert foo.txt

Ask your perforce admin to remove the lock by issuing

p4 unlock -f <file>

PS: To reuse the departed user's license, your perforce admin might also want clean up the files left opened by him. He can revert the pending edits if they are useless or transfer them to another user via "p4 reopen".

The "reopen" and "revert after reopen" can also be performed by ordinary users.