What exactly are you afraid of?
Let me put your mind at ease. Many people run their mouths about substrate induced impactions. However keep in mind, most people will not cough up one nickel for their snake to see a vet.
In other words, while snakes die all the time - for a variety of reasons - most owners have no clue as to why their snakes pass away. Most of these deaths do not involve substrate.
Most people make ASSumptions, because they won't pay for a necropsy.
If many of these people who wring their hands about bedding caused impactions actually talked to a reptile vet, they'd know that impactions caused by wood substrates are actually extremely rare.
Snakes often die because they get stressed. They get stressed because they are not kept correctly. Snakes often die because people hoard them and do not practice quarantine procedures. Snakes die because while many people will shell down some serious cash to own the latest morph, they won't pay $100 to see a reptile vet.
I'm very curious about your timeline. If you choose to feed your snake in a tub - and you are running late for school - why not wait until you come home to feed the snake? Not that it matters anyway, but bear with me for a sec:
If you think that substrate ingestion is so worrisome that you had to trot out the heavy emotional firepower (the dreaded "tears" emoticon") why did you not just wait until you came home? What compelled you to rush this? Why could it not wait?