Bag was at OP's feet, shifted back into foot space of pax behind who may at that point not have boarded yet, when that pax boarded they alerted FA.
IMHO FA should have had the presence of mind to ask the pax in the seat ahead (OP) and this is a customer service failure. Of course pax behind was right to alert FA (or perhaps should have asked OP first, both options are acceptable to me), the FA should have evaluated the situation a bit more critically however.