Although the Bechor Shor’s read of the verse is compelling, it runs into one significant obstacle. The Gemara in Sanhedrin 67b says explicitly that the magicians were unable to create, not remove, the lice.
Sometimes the Bechor Shor sets aside the midrashic approach of the Talmud in favor of a more pshat approach, more true to the simple and original read of the verse. For example, in Bereishit 48:22 when Jacob says that he seized the city of Shechem with his sword and shield, the Bechor Shor writes that this means that Jacob conquered Shechem in war. The Midrash, on the other hand, understands the sword and shield of this verse to be symbolic of prayer. It is important to note that in this instance the Bechor Shor is not rejecting the interpretation of the Talmud as much as he is choosing to apply a pshat approach instead. However, with regards to the lice, the Talmud in Sanhedrin is seemingly providing the pshat, simple read, of the verse. The Talmud is saying that the magicians tried to create, not remove, lice.
The simple answer could in fact be that the Bechor Shor argues with the interpretation given in the Talmud. This would not be unprecedented for the Bechor Shor. For example, in Bereishit 28:11 the Torah states that Jacob took “Me’avnei Hamakom, from the rocks of the place” and put them under his head. The Talmud in Chulin 91 says that Jacob took many rocks and put them under his head, and they then all merged into one big rock. However the Bechor Shor says that he only took one rock originally. The Hebrew word Me’avnei means that Jacob took one rock from many rocks, not that he took many rocks.
So perhaps here too with regards to the lice, the Bechor Shor argues with sages of the Talmud.
Or perhaps he reads the passage in the Talmud differently. When the Talmud states that “a demon cannot create an entity smaller than a barley grain” in reference to the inability of the magicians to replicate the plague of lice, maybe the word “create” can be understood more broadly. The demons cannot effect things smaller than a barley, whether creative or destructive. A proof for this approach could be in that the Bechor Shor does not even directly quote this passage in the Talmud (neither does Rashi). Rather he writes that, “a demon can not control something smaller than a lentil.” If the Bechor Shor sees these two statements as one in the same, then that would certainly solve the problem.
It’s very interesting to note that while the Bechor Shor arguably is disagreeing with the sages of the Talmud as presented above, he nonetheless comes to their defense in his very next comment!
Once the magicians are not able to replicate the plague of lice, they declare that the plague must therefore be the “Etzbah Elokim, finger of God.” The Rashbam writes that this means that the magicians saw the plague of lice as a matter of nature. It is not that Moses was able to miraculously generate the lice. Rather, they were a product of the natural order of the world. The Bechor Shor sees this approach of the Rashbam (though he does not quote the Rashbam) as being against the Talmud and problematic. He writes that one should not argue with the sages of the Talmud. The Bechor Shor says that the magicians saw that their magic did not work on things so small and therefore came to the conclusion that Moses must have been acting through God, and not sorcery.
While the Bechor Shor is ready to offer interpretations to the Torah that are not always congruent with the approach of the Talmud, nonetheless he stands ready to defend the Talmud when needed.