This is a "theory" I have heard many times, and I just can't abide it. First of all, it assumes people who followed Jesus just happened to carry around enormous amounts of food that they kept hidden from their fellow followers. It assumes that good people, interested in God's word and listening to the Messiah would not already be predisposed to sharing food with a hungry person - something that just about every Old Testament figure does without having to have Jesus "make" them do it (and something that people would do as a matter of culture in those times). It assumes that the sacred authors, who were familiar with scripture that distinguishes between God "hardening" or "softening" someone's heart and a true miracle, deliberately mislead us in this instance.
But even more than that, once we "explain away" miracles where do we stop? If we say "well, the sacred authors wrote that the five loaves and two fishes fed the five thousands, but I think it was just sharing" where do we stop? Do we say "well, the sacred authors wrote that Jesus cast out demons, but it was really just epilepsy?" Do we then say "well, the sacred authors wrote that Jesus raised the dead girl but she was just sleeping?" How about "well, the blind man wasn't really blind from birth?" Are we then to become the Pharisees? How about "Jesus wasn't really dead, just injured and he healed in three days." Perhaps Jesus didn't really do any miracles, but was a good talker. Well, perhaps then He didn't redeem us from sin.
If you can't believe that the one through whom the universe was created could create fish and bread when He wanted to, perhaps you just don't believe in the creator at all. If you're not going to believe that what was written is true (by authors who believed it to be true to the extent that they gave their very lives for it, by the way), just say "I don't believe" and be done with it. Stop trying to whittle away at the edges. As for me and my household, we will serve the Lord.