Don't worry, it's nothing. however
Sorry, there's no way to ID a pill without an imprint. All Rx and OTC drugs in the US are required by law to have an imprint, otherwise it could be a vitamin, herbal, energy, diet, foreign or illicit.
That's a waste of time, first, most pharmacists are hopeless at IDing pills, second, there's thousands of different round white blank pills, how could ANYONE tell one from another? They can't, it's impossible.
small, thick, round white pill w/no markings 
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