It's now under the History tab of a client record.

That just looks at the usage logs for that individual computer. You used to be able to do a mass search and see all results for a username.

Gabe Shackney
Princeton Public Schools

Probably a side of effect of full logs gone, but supposedly planned to come back at some point

https://jamfnation.jamfsoftware.com/featureRequest.html?id=1357

Yeah, man, that's been gone since version 9.0 and hasn't come back yet. See the FR above that @CasperSally posted for the details.
Although I didn't use that often in version 8, it was still handy to have in those times when I needed it, so I hope it comes back in some capacity.