I don't know about this. I have been attacked before in the wild and I was not able to revenge them. Maybe it was because I didn't revenge them for a period of time and it just disappeared from the list?
If the person who revenged you did NOT defeat you then you will not be able to revenge them back, however, if they did defeat you, then you can revenge them back
There's no point in revenging somebody who didn't defeat you in the first place