I'm not sure if low-rez scans of just the maps constitute fair use or not. Anyone know?
I'm not prepared to cite any legal cases, but I believe one could have a fair chance at making the argument successfully if it were a one person to one person transfer.
The Fair Use provisions of the US Copyright law, for example:
In determining whether the use made of a work in any particular case is a fair use the factors to be considered shall include —
(1) the purpose and character of the use, including whether such use is of a commercial nature or is for nonprofit educational purposes;
(2) the nature of the copyrighted work;
(3) the amount and substantiality of the portion used in relation to the copyrighted work as a whole; and
(4) the effect of the use upon the potential market for or value of the copyrighted work.
Given that 1 would be generally non-commercial (assuming the guy isn't a "professional" DM, that the maps are expected to be used for the game, that they're a small portion of the work, and that it's unlikely putting the maps out would effect the value of the work which is out of print anyway, a lawyer would be at least able to pass some muster in making the argument.
Obviously, you may have other rights in other jurisdictions, some may even grant you the explicit right to recover the damaged or missing portions of the material, but you'd have to consult a local legal authority to know.