Do you mean RCI Points or RCI Weeks when you say you found out the week was deposited in RCI?
If RCI Weeks then this was something the seller had to proactively initiate themselves in their RCI account and it would be hard to believe they didn't realize the next years usage was not available. This is also something that should have been flagged on any Estoppel.
But if you are talking RCI Points this is not an uncommon problem on resale weeks in the RCI Points system. Especially if the new owner is not a RCI member in RCI Points, or doesn't want the specific week being purchased to be in RCI Points. I know many people love and effectively use RCI Points, but I am not an RCI member and don't want to be.
The problem I have found with buying weeks in RCI Points is that many longtime owners who are selling their weeks (especially thru 3rd party resellers on Ebay and elsewhere) is that they don't even understand anymore how their RCI Points membership works. RCI will automatically take an owners week and deposit it in points at something like the 12 month or 11 month out mark unless the owner explicitly informs RCI that they plan on using their home week and do NOT want it deposited in RCI Points that year. So sometimes owners who are older or who haven't really been using their timeshare for some years don't realize that when they go to sell their week they need to either (1) end their RCI Points ownership for that specific deeded week they want to get rid of, or (2) make sure the next year's week is not automatically sucked into the RCI Points program so the new owner can decide what they want to do with the usage going forward.
And frequently Estoppels will NOT give you the correct information when it comes to deeded weeks in RCI Points because there is a disconnect to visibility between corporate Owner Services, the specific resort, and the Reseller / Owner / Buyer. You typically find out only AFTER you own the week and you get a call from the resort telling you that your usage week was deposited into RCI Points many months ago.
What is even worse, is that even when you are the new owner and the deed and unit has been transferred to you, RCI will not pull your new owned week from their RCI Points program. That is because their records still show it as owned by the previous owner and you can't speak for the previous owners RCI Account. This makes a certain amount of sense from RCI's standpoint that you can't modify another owner's RCI account, but it can create a logistical nightmare for you if you are the new owner and force you to jump thru multiple hoops to fix the problem. So you either have to go back to the former owner and get them to help you after the fact remove the week from their RCI Points membership, or you have to work with your resort and have them send RCI a notice to remove your week from their RCI Points program. That way if RCI tries to pull it into their Points program anyway (and this has actually happened to me), you have a record with the resort and the resort will tell RCI that they have to fix the problem on their end and assist their member who traded into your week via Points and find them a replacement because they weren't supposed to take it. So will get your deeded week in that case, but will have to get involved and work with your resort to "take it back" from RCI.
And many times it isn't the resellers fault entirely. Some legacy owners don't tell them (because they don't even remember anymore how the RCI Points program works), the Estoppel frequently doesn't show the problem and shows the next years use as available, and many resellers don't have experience with this specific issue, so they don't even understand how RCI Points automatically takes the weeks almost a year in advance, until the problem comes up after the transfer.
It can be a mess. I have dealt with this with multiple resellers. Fortunately in every instance I was made whole one way or the other, and in no instance did the resellers ever do this on purpose. They didn't know either.