I purchased tickets through the Target Circle/Tripadvisor offer back in October and went through Rakuten. I received an email from Rakuten shortly after confirming the cash back, and I double-checked to make sure it was in my Rakuten account, which it was.
Now, when I check my Rakuten account, there is no record of the cash back, or even the shopping trip. It hasn't been paid out by check either, it's just vanished. I submitted a missing cash back form, and I'm waiting for a response, but I'm curious if anyone else had their cash back just disappear.