total bullsh*t. as others have pointed out, there were a few options to try if the author insists that a cauterized wound can't be healed.
just another lame attempt to make things hard for the MC without putting any thought into it
I have to agree, not a fan of you having him lose his arm. you're not a rookie writer anymore...be better than that! now that I have to pay for chapters, I'll give it a couple more to fix his arm before I drop.