Every time an Impersonate is attempted, a log entry is saved to the impersonate.log in Blackboard. Depending on your Blackboard Instance's log rotation settings, these may be backed up daily or weekly. Impersonate Logs can be retrieved similar to all other logs in Blackboard, from the Administrator Panel > Tools and Utilities > Logs. Impersonate logs are considered System Logs and are saved as such.
2017-09-01 08:26:14 INFO Impersonate:55 - Impersonate Successful!
2017-09-01 08:26:14 WARN impersonate_jsp:119 - "lwoods" is now impersonating "sponce_16"!
2017-09-01 08:26:26 WARN Impersonate:92 - Impersonate User Level Check FAILED
2017-09-01 08:26:52 INFO Impersonate:88 - Impersonate User Level Check Passed
2017-09-01 08:26:52 INFO Impersonate:55 - Impersonate Successful!
2017-09-01 08:26:52 WARN impersonate_jsp:125 - "sponce_16" is now impersonating "715305272"!