While this is interesting, converting to a child's sippy cup (i.e. a container that a diamond won't fall out of):

> When you turned the sippy cup upside down on the bed, the diamond likely fell out of the thimble, as it was not secured inside the cup. Since you didn't mention picking up the diamond after turning the cup upside down, it's likely still on your bed or somewhere around it, where it fell out.

Moving to a more obviously sealed container like an "unopened beer can" still puts the diamond on the bed. But if you remind it you didn't open the can, then it gets it.