The general rule I've seen applied is if either the fork or the frame has some critical damage that would diminish the value of the frame, then the two are separated.

In this case, my guess is the seller believed the locking fork would go for a premium, when, in fact, it only has a single bid.

The locking fork likely means this was a commuter bike, rather than a track bike. Possibly a 3 speed. I think that frame has fender mounts that the $2000 bike did not have.

If you really want the frame, then go online when the auction is ending. Put a bid on the frame in the last 10 seconds.

If you win the frame, then 3 minutes later put in a bid on the fork for the maximum amount you would pay (knowing you won the frame).