As has been previously discussed here, by me and others, there is an interstate compact that some, but not all states belong to. These seem to be clustered in the Midwest. I do not know all the states that are members.
Here is what happened. Top Hat is required by the state of Missouri to report out of state sales (not subject to sales tax in Missouri) to the State of Missouri. Missouri then shares that information with other states that are members of the compact. Michigan is one. I know that Illinois and Wisconsin are and I am certain that there are others.
This is the same buzz saw Iwan Ries has run into. It may be a distinction without a difference to those in the position of the OP, but Top Hat did not report him to the state of Michigan. Missouri did, using paperwork that Top Hat has to file to stay in business.
This has been going on for several years now. Nothing new.