[T+Z-Tank]

Was it a white, almost translucent piece that you saw? Or did it have the same colour as your shrimp? If it was white, it was likely just part of a molt. Shrimp molt (shed their exoskeletons) as they grow, and right after they molt they tend to go into hiding until they redevelop their exoskeletons.

That said, aside from otocinclus, any fish can eat/target/harass shrimp to the point that they die. Some are a little less likely than others, but it can still happen. Even if you had no issues for years, it can happen overnight.

pictured above, it was bright red and even had what looked like “shrimp meat” for lack of a better term

 

[T+Z-Tank]

I agree with @sm1ke but it doesn't explain why it was on the floor out of the tank. Do you have any pets roaming your house?

Sorry no it was on the floor of the tank, the picture was from after it was taken out