LonnyRJones

Yes if you use system restore to go back a few days or more the pc will be infected although if an antivirus deleted anything there they will not work.

After we Analise logs from your colleagues and clear the virus/trojans
as a last step we will clear system restore but turning it off then back on again.
It would be best if all the PCs on the network were disconnected and obviously don't share removable media

Let me know when they post logs
How many colleagues are there ?

Using explorer look in each usb stick for a file named boot.exe and idstick.exe, if found submit it to the URL i posted please