Had this happen twice today on version FMPA 14.0.2
Working on a new script and when clicking back into the new script which is at the bottom of the list, it vanishes from this list.
It's not in the folders and not findable via the search function.
Have to restart script workspace to get it to reappear.
Inconsistent, cannot 100% reproduce.
Pattern seems that it needs to be at bottom of list and just been edited, run system in browse mode, click to edit mode and then attempt to enter the script whereupon it vanishes again.
As I say, this is inconsistent and unfortunately don't have too much time to gather reproduction steps.