I placed syrup in a baggie inside my TBH and in one day it is gone. I placed another baggie inside today, but also put some syrup in shallow open container on top of the TBH. Temperature is ~65 today, bees flying everywhere.
Why would they not touch the syrup on top of the hive?
Most likely, they're getting 'real' food from foraging. It would be interesting to see if they've consumed the baggie as well. If plants are blooming where you are, I wouldn't worry about it much.
-T