I put a hold on an item and it showed up as "taking it". Then I checked under my holds and it had disappeared . I tried again -- same thing.
If this just happened in the last day or two, it is because the library database was down for some hours and is still not processing holds properly. They are working on it right now. If you provide your library barcode, I can see if the hold appears on the staff side. If not, you can try placing the hold again later today or tomorrow.
Sorry about the inconvenience!