It is hard.. the only thing I can think of to help you is to trust - over time. Oh, and follow your gut too. If someone feels wrong, they probably are.

The time thing.. your first example - if this guy knows things about you, and say, in 3-6 months time he has done nothing with that information that may hurt you, then you can use that time as a signal that you can start to trust him. Know what I mean? It's kinda like proof that he maybe trustworthy and then perhaps you can start to relax in his company.

The second example, I don't think that's too much of a trust issue, as Lynn says, it's good to be street wise! I think I may have thought the same, even if for a brief moment. I think when it comes to losing wallets, it's natural to be suspicious of the person who was near you?

Good luck to you and I hope you find your way. I guess that we can expect to get our trust broken at times and I think it's trial and error - we get to learn certain types of people and keep those bad ones at arms length. Not 100%, but I find it helps.
Hugs.