This is a good reminder that many of the record collections accessible at FamilySearch.org do not belong to FamilySearch, and are made available through a contract with an organization that has legal control of those records. As contracts are added (or terminated), sets of records suddenly appear (or disappear) from the collections on FamilySearch.org.
What happened to the (fill in the blank) records? The answer may be that the government (or other agency) got a better offer and decided that selling access made better economic sense than giving the access away for free.
So we cannot guarantee that the records that are available in FS today will be there next week. We should teach our patrons to make the best of the opportunities currently available.
FamilySearch will negotiate the most generous accessibility possible. In some cases the records are accessible to everyone. In other cases they accessible only at a FHC (in the Portal, not in a personal account). In some cases they are only accessible to Church members, whose tithing finances the operations of FamilySearch. And some items can only be viewed by one person at a time. Other items or entire collections may quietly disappear. But it is not by our choice. We are doing the best we can for our patrons.