If someone's wheelchair was taken, they would report it to the CMs in the area, who would let security know. WDW would offer a park rental wheelchair until the personal one could be found.
BUT ----
the only wheelchairs I've ever heard of being taken were the park rental wheelchairs. In many of those cases, it's probably taken by mistake by someone else who rented a wheelchair at the park. It's not likely that someone would mistake someone's personal wheelchair for the one they rented in the park, so chances of a personal wheelchair being taken by mistake would be pretty small.
If someone was actually looking to
steal a wheelchair, they would be more likely to take one of the park rental ones for a number of reasons:
- There are a lot of park rental wheelchair and relatively few personal wheelchairs.
- There are so many park rental wheelchairs, it would be easy to 'blend in' if you took one. It would be a lot harder to 'blend in' if someone took a personal wheelchair.
- Someone trying to take a wheelchair would not know when the owner/renter of the wheelchair might come back. If the owner/renter came back and saw the chair being taken, it would be easy to claim a rental one was taken by mistake. It would be really hard to try to claim a personal wheelchair was taken by mistake.
- The things that make the personal wheelchair fit the owner would tend to make it inconvenient/uncomfortable to someone else.
The first year that we took DD's manual wheelchair with us, we worried about someone taking it and actually did bring a lock. But, we never used it.
For all of the movies and shows, you will be sitting in the wheelchair.
There are some rides that have a wheelchair car and you could stay in your wheelchair for those if it is easier for you to not transfer.
Even if you do transfer or for rides where it is necessary to transfer, your wheelchair will be parked at the exit, as has been already mentioned. The CMs usually park them out of the exit path, but very close to the exit.
Most people getting off rides probably don't even see the wheelchairs, even though they are often in plain sight. People are focused on getting to the exit and don't really notice anything except getting out. Even if someone did see the wheelchair parked there, they would have no way of knowing if the owner of the wheelchair is in one of the next ride cars.
So, I would not worry about the wheelchair being taken. I would suggest you not leave anything of value on it. We usually leave DD's backpack on her wheelchair, but it has nothing of value in it (unless someone is looking for extra clothes and snacks).