First off, I am appalled that the seller didn't know whether the snake had eaten or not. Any seller with a shred of decency should know if the snake had eaten. Plus, no decent breeder would sell a 12 DAY old boa. Most quality breeders insist that their babies have their first shed and eat at least 3 times before leaving at, roughly, 4-6 WEEKS old (or older). I don't mean to scathe the seller, but seriously he should have known better. As such, I wouldn't bother calling him for more info....
Anyhow, let's assume this baby hasn't eaten yet. Boas are not known for having feeding issues so I doubt you'll have too much trouble. Let's not ask for trouble and assume that he'll eat when you offer. If he doesn't, let us know and we'll go from there.
First off, boas are not ball pythons and should not be fed like them. Smaller prey items are better. Most reputable breeders start neonates on mice rather than rats. The fat content in rat pinks and pups is generally too high for boas and they don't seem to grow as well. They might grow faster on rats, but not better. Slow-grown boas are healthier in the long run.
Here is what I would do. You've had him for 2 days so give him the rest of the week to settle in, relax, and get hungry. 5-6 days from now, try offering a small peach fuzzy mouse. I would offer live if you can, but if not go ahead and try f/t. Offer the prey when it's late evening and nice and quiet. If he doesn't eat, leave the fuzzy in his cage (a live one won't be a threat to the boa - the mouse is too young at this point) and leave him alone for a few hours or even over night. Generally, they instinctively know the smell and he'll likely take it when he's ready.
If his first feeding is a success, you can then think about a schedule for him. Such a small baby should stay on mouse fuzzies for a few weeks or even a few months, depending on growth rate. And do NOT feed any more frequently than every 7 days!! Boa babies can go a long time between meals. Many good breeders feed every 10 days right from the get-go.
Hope this is helpful to you. Post a few pictures - we like pictures!![]()