Where in your post did you say this was advice about an informal agreement between friends?

Here's a little tip for you, nothing is regarded as a formal proceeding unless that route is specifically mention. If you are going to post here, you should really be a little bit more knowledgeable on the subject. YOU assumed that, when there was no mention of it. You know what happens when you assume don't you?

that's theft of property

You honestly have no idea what you are talking about and its really showing. Let me teach you something, lets say OP and his friend both personally accepted that agreement. His friend doesnt move forward with litigation against OP, in favor of the personal deal they made. I assume you will be able to guess what that makes your previous statement, but I might be asking too much out of you.