A local object disappeared in ABAP from $TMP package
You cannot restore or track local objects if they were deleted. There could  be any reason from that you have mentioned. Better ask collegues / basic team if they made some changes.
Try to look up the table TADIR (Directory of Repository Objects) to check which local development objects exist. Use SE16 / SE16N transaction with condition DEVCLASS = $TMP, additionally AUTHOR to include only objects from specific user, OBJ_NAME = Z_ABCD* to restrict the program name.
You can also check the table REPOSRC (Report Source Code), where reports source code in RAWSTRING (DATA field) is stored. Filter on PROGNAME, CNAM (username) to check if the source sode is available on the system (there are also several views avaiable for this table, TRDIR, D010SINF).
If the program were assigned to a package / transport and deleted, than you could find it in TADIR with a deletion flag DELFLAG = X, and also in the table E071 with OBJFUNC = D in case of a transport assignment. Local objects just get deleted from the repository tables.

There was a local report in the $TMP that is "disappeared" somehow. I did not delete it, but can't see it in SE80 anymore.
What could be the reason?
Somebody else has deleted it. The system has been resetted somehow to an older backup state. Are any other reasons possible?
Is there a possibility to see in the traces what has happened or are there any other (better) tracking possibilities?
Unfortunately I don't know what was the exact name of the disappeared report, but I know the beginning of its name (like Z_ABCD_...)
