If the printer is connected via USB check to see if the user changed the USB port the cable for the printer was plugged into. If the user plugs the cable into a different physical USB port then the logical printer port in Windows will be changed to match.
Ideally you never want to rely on user machines for services that other staff will need access to. I would consider connecting the printer to a print server. Assuming the printer is USB, these are readily available (
USB Print Server) Once you've assigned the print server an IP, you can then setup user machines to print to that IP. When each user logs into TS they will connect their local printers and be able to print without issue.