Hello, hope this will help anyone.
I found out how to reset Chip's spleen quest if you forgot to found the spleen within allotted time.
I'll need F2SE. So:
1) back up your savegame
2) open f2se and choose your save
3) go to GVAR tab and edit:
367: GVAR_SAN_FRAN_SPLEEN to 0
448...
