A sad day indeed. After researching this vigorously Ladyhawk, this was completely the store owners fault, and more than likely a result of being ferried across a long distance with a full stomach.
Snakes regurgitating is not a good thing. If a snake is kept too warm, usually over 85 degrees, the heat acts as a catalyst for the decomposition of a food item ingested. The reason for this is that negative bacteria begin to break the food down faster than the beneficial bacteria found within the gut of the snake can digest it. This is usually manifested in the snake as a visible bloating in the gut, usually the result of gasses which begin to form as a by-product of the bacteria.
After a while, the snake's internal alarm tells it to expel the decomposing food item before the bad bacteria spills out into the gut causing another slew of complications. I'm sure the bloated food item also causes a considerable amount of discomfort and could contribute to the regurgitation as well.
Long story short they should not have let you take the animal on that trip after a feeding.