BIG-IP : deleted data-group/file contents are re-appearing in re-created data-group/file of same name

Does BIG-IP somewhere retain contents of deleted data-files - perhaps in a hidden cache file or a database ?

there is .trash_bin_d under /config/filestore. anyway, i think it may not relate to your issue. if the issue is reproducible, i think you had better open a support case.

[root@ve11a:Active:In Sync] filestore  ls -al
total 40
drwxr-xr-x  5 root root 4096 Jul  7 07:12 .
drwxr-xr-x 24 root root 4096 Aug 10 04:02 ..
drwxrwxrwx  3 root root 4096 Apr  8 20:34 files_d
drwxr-xr-x  2 root root 4096 Jul 31 19:50 .snapshots_d
drwxr-xr-x  3 root root 4096 Aug  6 06:47 .trash_bin_d