This is gross, but, this summer my cat killed a bird and took it in our garage. I didn't discover it for awhile. When I did finally, I lifted it into a plastic bag. Many maggots were under it, and were left with goo and a few feathers. I was gone like 30 seconds to reach for a dustpan and little broom. I was amazed that they'd headed out in all directions. I couldn't even sweep them all up, they really traveled fast enough to disappear behind other stuff in a corner.
So, I decided, many from that pizza and bag were probably gone by the time LE picked it up at Amscots. I hope enough were left for LE to do what they have to do for testing.