YES and NO. The first thing to do is go back and review your paycheck to see if in fact the dues were deducted. If not, there could be several different explanations. The Company is responsible for taking the dues out of your check, not AFA. This means, the Company could have made a mistake.
Another explanation could be that you flew low time and/or dropped trips. Since Union dues are the last thing to be deducted from your paycheck, there may not have been enough monies left, after your other deductions, to cover the amount of the union dues obligation.
Lastly, remember that if you were on any kind of unpaid leave, there would be no paycheck from which the dues could be deducted.