Here are some possibilities for the last modified date being updated but no command placed in the recovery file or showing in the TSSAUDIT CHANGES report:
1) A TSS LIST(acid) command was done on the acid and the acid had an expired permit. (An expired permit would be a TSS PER(acid) xxx FOR(nn) or UNTIL(mm/dd/yy).)
2) If the acid in question owns a resource, when the resource is permitted to another acid, the last mod date will be updated because the WHOHAS pointer is placed in the acid.
3) TSO signoff will cause an update to last mod date if the user changed any of the fields on the TSO signon screen when he last signed on.
4) If the user signed on and entered an invalid password, the next time he signs on with the correct password, the acid is modified to reset the PTHRESH counter.
5) If using multi factor authentication and there is a signon error with an incorrect token, the last modified date will be updated the next time the acid signs on with a correct token.
Also, if CPF is down between 2 nodes, the commands to be sent are kept in the CPF recovery file. Once CPF is re-established between the 2 nodes, the commands in the CPF recovery file are sent.