this word was touched on in passing a few years ago, and I wwftd it (how's that for verbing a noun?) with no citations as follows:

the worthless word for the day is: anagapesis

rare {so rare I have no etymology or citations}
[prob. from Gk agapé, love] /an eh gap EE sis/
a loss of feelings for one formerly loved

I'd still give a virtual sawbuck to find it used in the wild.
(it can be found on a raft of hard-word lists.)

-tsuwm