gold eye - Your coin is not an unstruck planchet as it has been struck on one side. An unstruck planchet would not have been struck on either side.
Your coin is quite nearly impossible to have come from the Mint in its current state. Without having it in hand to weigh I would presume that someone, for some reason, altered the coin enough to remove the reverse details and the reeded edge.
However, don't give up yet. You need to weigh the coin with a precision scale. If you do not have one visit a local coin shop or a jeweler and ask if they could weigh it for you. A properly struck clad dime as from the Mint will weigh 2.27 grams. If the dime is of the proper weight then you have quite the error and things will need to be taken from there.