If you are logged in to the OPAC, the hold button is gone until you click "View all the physical items." This doesn't appear to be the case when logged out, however, where the hold button appears right away. To recreate 1. While logged out, search for a record with enough items that the holdings table is hidden by default. 2. Observe that the Place hold is there as expected. 3. Log in to the OPAC. 4. Search for the same record. 5. Observe that the Place hold button is missing. 6. Click view all physical items. 7. See that the Place Hold button is back. I can only speculate, but this may be related to Bug 34886. I'd argue that if any items on the record are able to be reserved, it should appear, but at the very least it should be consistent.
This is a duplicate of Bug 13654 which was closed as "WONTFIX," but it's not clear to me why?