If it puts your mind at ease, the only way to gain 10 lbs of fat in 5 days is to eat 7,000 extra calories per day (in addition to your usual maintenance calories). If you ate like 8,500 calories per day, 5 days in a row, you would remember.
Swelling, on the other hand, is an easy way to gain fluid weight really fast.
Hope you heal quickly and start feeling back to normal really soon! Once you get through the awkward first several weeks, I'm sure you're going to be thrilled with the results.