Note that there is no mention about the backs of the cards. Discovery at the table of a red backed card in an otherwise blue pack is not a problem, the first time. It only becomes a problem when it happens session after session and some players know what card the red backed card is.
The finding of a red card together with 13 blue backed cards could be an indication that the red card has been held up in the hopper of the dealing machine. Try checking the previously dealt board in case a card is missing.
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