Yes, assuming it didn't freeze inside your garage, it could have survived. If temps in the garage got below freezing very much, I wouldn't expect it to survive, unless it was well insulated inside the bucket (wrapped, buried, etc).
Here's an article about how to store your canna, if you want to keep this one for next year:
https://home.howstuffworks.com/how-to-st ... -bulbs.htm
If it got planted in the spring, I wouldn't expect it to take so long to sprout, but that partly depends on how dried out it got in storage, how deep it was planted, etc. I suppose stranger things have happened!
A bird is still a possibility, but chances of that are higher if your neighbors have some cannas.