Many, many thousands of pressure cookers are sold every year. Terrorist attacks are extremely rare. Millions and millions of backpacks are sold every year. The intersection of those two products isn't helpful. The base rate theorem dictates that pressure cooker sales will turn out to be a very poor signal for terrorism.

This article posits (or is trying to sell you on the idea) that the FBI watches for pressure cooker sales on the Internet and dispatches teams of extremely expensive FBI agents to investigate them. Stipulate that the FBI has access to that information (I don't think they do, but whatever). What the FBI isn't going to do is compromise sources and methods in a pressure cooker dragnet. They are mathematically assured not to find terrorists that way. But they'd make a huge amount of noise. They don't burn sources for no good reason.

I don't buy this, at all.

Also not helpful, if you're trying to sell a hoax: the too-vivid callbacks to the Boston bombers, and to the FBI's television show image.

Later

Note also that this story wants you to infer that the FBI told her husband that they were following up on Internet search leads. Not only did they roll trucks to a residence to do a search that was almost mathematically guaranteed to come up blank, but when they did that, they hinted around at the secret program that got them to do it.