I have never heard of anyone actually observing bees moving an egg. REmoving an egg, yes. Carrying one around, maybe, but putting one in a cell, no. There are people who think the only explanation for something they have observed is that the bees moved an egg. Always in these situations thelytoky, which has been observed, would also explain it. Choosing between a never observed phenomena and one that has been observed many times in many places for many years I'd choose the observed one as the most likely.