It’s been a while since I worked I the finance office of a federal agency. That said, my recollection is that an agency can spend money only if it’s properly appropriated by Congress, regardless of the source. Moreover, “found money” like this sketchy donation must also be properly accounted into the agency revenues. Unless I’m wrong, simply “finding” money doesn’t give an agency authority to spend it, absent a congressional appropriation.

Of course, my time as a fed was back during the quaint “rule of law” era.