Sorry if this is in the wrong forum. Let's say, hypothetically, I go into a grocery store,
find a small container of Planters peanuts, and stuff it in my pocket in one of the store's blind spots. Nobody sees me do this. I then attempt to leave the store, but a security guard notices my pocket is bulging. Even though he did not see me conceal anything, would he be legally able to stop me and search me, based on the fact that there is an obvious bulge in my right front pocket?

Can he stop you? Yes. Can he search you? He's not supposed to, he's supposed to detain you then if you don't consent to a search he calls the pigs and they'll search you when they show up.

It's not really about what he can do though, it's what he will do. He'd probably see the bulge in your pocket and either:
-Not do anything, after all it's not a lot to go on.
-Call you out on it, at which point you keep walking and he most likely won't do shit.

It's some peanuts from a grocery store, it really shouldn't be that hard...

Sorry if this is in the wrong forum.

Bad Ideas Fraud, vandalism, torture, theft, revenge, scams, and other bad ideas.

You're in the right forum.

Why the fuck would you steal a packet of fucking penauts?

Also, my pocket usually bulges because my wallet is fucking filled with coins and I've never been stopped by security or asked about it.

Peanuts are just a hypothetical example. It could apply to anything...