I had a similar issue about a month ago on an ATL-LAX flight. Try asking for a CS manager. They may be able to offer a one-time exception to the rule especially based on the circumstances with which the delta dollars were promoted (i.e. Gate Agent said to use it as a gift as stated above). They will mark this in your FF# so its a one-time fix.

The T&Cs clearly state now that it is only for the person flying. However, if you buy one ticket (such as through your corporate TA) and then attempt to purchase a new ticket and link the PNRs, then you will be able to use the certificate (because technically your flying as well).

As always, YMMV.

Long time lurker, hope this helps!