Fuel Tank FOD
Many strange things have been found in aircraft fuel tanks.
I once had the resposibility of launching brand new shiny ones for the first time. Swarf and lost tools were a repeating hazard causing an ultra cautious approach.
Some things which managed to lodge in tanks were the plastic sealing caps which close off new fuel and air tubing. But the 'daddy' of them all was a vucum cleaner which had been used in a tank for cleaning up after a major inspection just before a shift change. Workers downed tools in situ and perhaps the next shift was expected to continue the clean up. Instead the tank was sealed. The vacuum cleaner was relocated following about 1500 flight hours.
Fuel tank sumps will normally collect items that don't float and hopefully the input filters to booster pumps will stop most small stuff which might stop a pump.
Take care. You or you refueller should have noticed that the chain was about to part company from either the tank cap or at the other end.