What happens if you don't "collect" an Oyster top-up or transfer in time?

With an Oyster Card, there are a few different ways you can arrange to top up, or collect additional tickets, or have balances transferred. Broadly, they are:

• At a station with a ticket machine (simpler things only)
• At a station at the ticket office
• Via auto top-up
• Arrange with the call centre of website, then collect from a nominated station when you touch in or out

For the last one, you have to nominate a single station to collect at, and it'll be available "from the next day".

I had a balance on an old oyster card I'd lost (but thankfully registered!), which I wanted to transfer to my new card. I knew I'd be in London the next day, so I used the website to request the transfer to my new card at the station I'd be starting at. Unfortunately, my idea of Next Day and TFLs differed, and it wasn't ready for collection when I got to London. I got an email the day after my trip saying it was then ready, which was too late as I'd gone...

What happens now? If you arrange to pick up some money onto your oyster card at a given station, and don't manage to collect it, what happens to the money?