VictorRuiz From my understanding the LTM does not automatically delete UCS files so if it was being deleted automatically it would be from a cronjob. You might try looking in /var/log/audit but that's a guess because I can't remember the exact file. The following link has some additional information on the different log files and what they store. You will have to go back through the archived log files and see if you can find when the UCS was deleted for the respective log which is audit.
https://support.f5.com/csp/article/K16197
Altocumulus
