It does happen but only by suprise.
A friend of mine just got back today. She was at OKW (studio) for 6/22, 6/23 but couldn't get 6/24 so when making her reservations she decided to take that one day at VWL. Upon her arriving at VWL about 11:00 she was informed that her reservation had been cancelled. With her confirmation in hand, she informed the CM and Supervisor that she was not in the system.
After the Supervisor doing some calling and checking, he asked that they go to the parks and just stop back later and he would have something for them. Well once they got their room keys and opened the door, the studio had blossomed into a dedicated 2br, yes she was upgrade to a 2br (for herself, DH and granddaughter).
What a surprise, so to all, 1) make sure you have your confirmation with you upon check in and 2) magic can happen at anytime when you're in Disney.