That has happened more than once to me, and after the third time, in a short while, they started shooting at me. I no longer pick pocket people, since it's hard to do and I'm trying for a Good Karma finish.
I just got the 'Stealth Boy' and was surprised to learn it's an aid and not a uniform. Does it last forever? Meaning, can I use it anytime I want. Any side health affects from using it?
I've been messing around a lot with the 'reverse pick pocket' feature. Sometimes I'll use it to my advantage by placing a better weapon, headgear, or armor on my target, and when they exchange their gear for the one that I gave them, I'll take their stuff...like the Kneecapper Shotgun, or Three Dog's Head Wrap....etc. I've got about 50 Stealthboys, but I've never bothered using one.
Lately, however, I've just been messing with named NPCs by placing different armor in their inventory.
The last time I saw Susan Lancaster, she was wearing Raider Sadist Armor....just like Lydia Montenegro, Ms. Primrose, Moira Brown, Lucy West, Jenny Stahl, and that drunk woman in Rivet City (forgot her name). Moira's guard Merc is wearing Brotherhood Outcast Armor (sans Helmet), and the chick that gives me gifts in Megaton is wearing Power Armor (sans Helmet). Little Maggie in Megaton is wearing Talon Combat Armor, and the Rivet drunk's son is wearing what looks like a scaled down version of Raider Blastmaster Armor, while the Priest and Diego have the full sized version of this same armor.
You lose some Karma ever time that you 'reverse pick pocket' someone, but I guess it isn't too much because I'm still shown as being 'Very Good'. Besides, you can easily increase your Karma by donating to the Rivet City Church, for example. I'll eventually get most of the folk in the developed towns to wear something different. This is just something that I'll keep doing to pass the time when I don't feel like killing anything.
Edit: I left out the most important part.....
I always save right before I try any of this, because it will often backfire even while Hidden, with Sneak at 100. It took one try, for example, to place a Brotherhood of Steel Helmet into Three Dog's inventory. It took many reloads before I was successful in stealing his Head Wrap.