In asking for help, you are often giving a gift to someone – exposing your own need and vulnerability (which can be hard), and giving them an option to shine.
You are not necessarily incurring a debt of any kind, but instead (when you ask in a genuine way for a genuine thing) are giving someone the chance to be generous.
You have the same opportunity to be generous in return. Sure, you can thank someone. Much better, though, is to let them know how their help helped – be very active here, very specific, and share your success, bathe them in that same warm glow.
You’ll feel better and they will too. Otherwise, they might feel like all they’ve done is howl at the moon.