The place to start is the concatenation of the CICS load libs from where your programs are loaded. Since the concatenation sequence is always first to last, the first load lib in the concatenation sequence that contains a copy of the program in question will be the library it is loaded form.
For more detailed info, I suggest you check with your CICS software guy. I do not know if you could get this info from your CICS monitor. (Its been a LOOOONG time since I worked on CICS)
By the way, if you are trying to cause a new version of a program to execute in an already running CICS region you will need to tell CICS to refresh the program. Your shop may use a special transaction to cause this (newCopy, or CEMT, or …).