What could a scammer do with just my signature?

I signed a form, and now I’m trying to decide whether I fell for a scam or not. Whatever way I look at the situation, it doesn’t make any sense to me, so I’m wondering if anyone else has more insight into this.

I was walking out of the supermarket, and this guy who was standing around the entrance called me over. He seemed nice, and I didn’t want to be rude, so I went over to talk to him. He gave me a spiel about voting for him for a public speaking contest, and how if he won they’d send him on a trip to Europe. Then he pulled out a list of magazines and asked me to pick six, and he said those six would be donated to either children, schoolkids, or elderly people, whichever I chose. During all this, he made smalltalk, and asked questions about where I was from, what I did, whether I was married, etc. At one point he called his friend over (who was trying to catch shoppers’ attention a few feet away), to tell him about one of my answers. At this point I took this to be a sort of school fundraiser thing (I remember doing similar things for my school), so I thought nothing of it.

He asked for my phone number and address, but I told him I wasn’t comfortable disclosing those things. Then he asked me to sign a form on a little pad to prove that I had actually “voted” for him and had requested the magazines to be donated. He also had me write scores (from 1 to 10) for how courteous he had been and so on. Then he ripped a pink copy paper from under the form and handed it to me, saying “Thank you, here’s the receipt for the magazines you bought.” I was confused, and asked what he was talking about, and he said my signature meant that I had paid for the magazines I had chosen. I explained that the way he made it sound, they were going to be donated by someone else, and that I wasn’t willing to pay any money. His response was “You signed a contract, you can’t take it back. Now, you look like a smart person, and if you know what’s good for you, you would just walk away now.” His friend then told me that it wasn’t a big deal, they would just void the form and I wouldn’t lose any money. And then they walked off.

I live in California, US. The form didn’t really have a lot of text on it, just fields to fill in for various information. I don’t remember if it had any company or other identifying information on it. I didn’t look at the receipt, and the guy took it back when I complained, so I don’t have it. This is the information I gave them:

• My job title (software engineer)
• My marital status (not married)
• The state I grew up in (not the one I was born in)
• My first and last name
• My signature

I’ve come up with four possible explanations:

1. It was all legitimate, the magazines were going to be donated by a third party, but at the end he heavily miscommunicated this. When I tried to take back my “purchase”, he became angry with me because people had been ignoring him all day, and he felt that I had lead him on and then changed my mind at the last moment for no reason.
2. It was all legitimate, and I was supposed to have paid for the magazines, but he forgot to ask for my credit card or bank information.
3. It was a scam, but he forgot to ask for my credit card or bank information, making it useless.
4. It was a directed scam; he had already gotten my other information through other means, and all he needed was my signature. Alternatively, he wants to sell my signature to some larger operation so they can cross-reference it with other information they’ve leaked. Although, if this is the case, I don’t see the point of him giving me a receipt, or doing half the other things he did.

None of those explanations make sense to me, but I just can’t think of anything useful he could do with just my signature. Since this happened, I’ve read about similar scams (public speaking, trip to Europe, donate magazines to children, etc), but people who fall for those always give out bank information. So my question is, what do you think this guy’s goal was? Is there any way he could steal my money or identity if all he has is my signature?