I have my first ever WL book en route to me so I looked at my wishlist and saw that it shows 2 versions of the book "on hold" but the other 4 versions of the book that were on my WL have disappeared.  I guess the book should go on hold til I mark it received, but then shouldn't all the versions have stayed on the WL???

Yes. The one version that was granted should have moved off of your wish list and the rest should have remained there, but placed on Hold by the system if they were tied together. If they were not linked by the system, then they'd remain there, but the system wouldn't put them on Hold. Make sure to resort your list a few ways to see if they are just not showing in the current sort or the search (that thing is flacky and doesn't seem to always work IMO).

If they truly disappeared, contact the Team by sending in Feedback using the Contact Us link in the lower right under Company and ask if they can tell you where the other versions went.

Now how did you make it this long without getting a Wish List book!?! That is so fun to get a wish granted!

OK, I did several resorts and the other versions still aren't there at all.

I got another WL book offer yesterday and it too has had some of the other versions I had WL'd disappear.

But, I had 6 versions of "The Book Thief" on my wishlist and suddenly it shows 11 versions on the list!