Number one thing to check when you take an action in a Cisco device and don't see a related event in LEM, does your device even log that event type? Run a show logging on the device, you'd be shocked at how little Cisco logs by default.
Thie below doc outlines some of the categories of possible traps you could send if you don't want to crank up the syslog logging level. I don't know off hand what level user account changes are but worst case you can set yourself up to debug, make some changes, and then review the logging to see what events you are interested in and how they show up.
Cisco IOS SNMP Traps Supported and How to Configure Them - Cisco