I have in the past, extended a lisp file with a short little app and then forgot about it.
Upon loading the main routine, the little app was loaded as well.
Later in development of a similar app, I found that I was calling a function or subroutine in a
different manor or for unique results.
However, if the old app was loaded first, it's definition would take precedence.
Check to see if your function is unique to the current Acad session.
Tony.