we're in the same boat with our 2 3/4 year old. She uses the potty all day at daycare, but waits to come home to poop. She asks for a pull-up so she can go hide and poop. I asked her pediatrican and (very experienced) daycare provider, and they both said that it's a simple case of "not ready yet". They suggested not to push the issue because then it turns into a control issue and she could do things like withold, deliberate accidents, etc.
So, for now, we tell her she can take off her panties and put on a pull-up when she has to make a poop. She is aware enough to know when she's going, and fortunate enough to be a very regular kid! Her big reward when she is ready is a trip to Chuck E Cheese. She knows this, and it motivates her to try, but I think she doesn't like the sitting position. She still likes to squat.
It will happen! Be positive and encouraging and patient. In addition to the goodie bag, the reward chart might also be a good idea, but researchers have found both tend to provide more of a short-term boost to motivation and fizzle out after a while. We discovered just that!