The "Argument from the Negative" Fallacy occurs when the burden of proof (YouTube video explanation) is improperly shifted and/or, because one item doesn't work, other plausible conclusions are prematurely omitted from the argument, too.
Example:
Cliff: That blurry trail camera picture is of a Bigfoot.
Matt: How can you say that? It could just as well be a bear.
Cliff: You can't prove that it's not a Bigfoot, so I'm calling it a Bigfoot.
(Who has the burden of proof here? Also, this might be a good example of Occam's Razor)
Example: Summer is not the best season; therefore, winter must be the best season.
(Notice how spring and autumn have been suspiciously omitted from the discussion?)
Example: 2+2≠5; therefore, 2+2=7.
(Clearly, our arguer just wants to come to the conclusion that 2+2=7 -- perhaps, he or she has an agenda and hopes to make a lot of money off of this conclusion. Obviously, a plausible answer is not even being considered here.)