Using airline voucher- how far do I have to dig?

[Heather Steen]

I have a faculty member traveling, charging non-sponsored funds, and also using a credit she has with the airline.  She didn't give any indication of what the credit was from.  How far do I need to dig to determine if a grunt originally paid for that credit, and then do I need to credit the grant if we're now using the credit for travel related to non-sponsored work?  I'm assuming I need to dig in and find out, and then move the charges if it was paid on a grant, but I can't actually find that in the older Covid-19 travel guidance I looked at, and the OVPR guidance has been removed from the web.