Had a WL book appear accepted, had the "waiting for member" message in the window. As usual I checked out their bookself to see if there were any additional books I'd like to order. Just so happen there were two addtional ones I needed to add to a series. It would let me add them, but not complete the order. Never had that happen. Tried it two more times, same thing. I thought I would just go directly to the members bookself instead of through the "order more from member" button. Turns out the self is on hold.  I never remember having a WL book go to a bookself on hold. I realize you can't tell when the book was actually posted and it could have timed out any number of times before it got to me so the member could have put their self on hold at any time.  But, why would  my request have gone to a bookself on hold? Even if they had put their self on hold after my order reached them, seems like it would have automatically set my request back to WL.  No biggie, I just canceled my order and put it on my WL again. I know that put me in the back of the line, but again, no biggie, it just made me 3 of 3 and my TBR pile isn't likely to get lonely any time soon so waiting is fine.  Thought it just a little odd.

If their shelf was on hold, you wouldn't have been able to see the books on it.  Also, if they were on Hold and an offer timed out, it wouldn't have moved to the next wisher but would have gotten held on their shelf until they took it off of hold. My guess is they posted it, then put their shelf back on hold and you just had the timing to look during the time in between.  No reason you had to cancel it though. Lots of us take our shelves off of hold, post a WL book, and then put our shelves back on hold. The WL book could have been a valid offer.

I would have sent them a PM about the other 2 books.

They probably took their shelf off hold just to get the WL book posted. Maybe they were in the process of putting it back on hold while you were looking at the Order More From Member button.  I would also PM them about the other 2 books.  If it's someone with budget concerns they might appreciate being able to send 3 books for 3 credits all at once. 

I frequently put my shelf on hold and unhold it just long enough to post a WL book. Sometimes I'll leave it off hold for a bit if it looks like it's going to time out otherwise it goes back on hold instead of to the next wisher in line. I do it mostly to stop the WL offers for a bit but some people can only afford to mail out a certain number of books each month and just unhold to post WL books when they have the money.