The LDAP should be server folks -- Active Directory. Chances are whoever manages the ASA's should have access to at least look in Active Directory to look that up. If they don't they need it.
I obviously don't know a lot about what devices you are using, but if you are using ISE, there should be some type of MNT device (Monitoring and Troubleshooting) -- which is collecting the logs and, hopefully, sending them to some type of syslog aggregate collection tool (splunk?).
Otherwise, there should be a device called a CAM (Clean Access Manager) that is collecting logs -- which may also be propagated to a syslog aggregate tool -- although with CAM's, you can pull the reports right out of them in a comma deliminated file (.csv) and go through them that way.
-- The thing that gets me is that it happens to two users no matter what computer they try to connect from, no matter what network they connect from, and other users can authenticate and gain network access on those same devices.
-- That is why it is rather perplexing. Pretty much saying it has to be something with:
- the IP pool they are getting an IP from
- their AD credentials
- their username
- something along those lines, if the information provided was fully accurate.
