Yep, if you can't remember anything more than that, you can consider whatever you had in that wallet lost then. It won't help you to think about what could have been.

But as a side note, you could give it a shot by going back through all your notes from that time, if you've got any. I'm in the habit of jotting down all sorts of stuff and little reminders on paper, and I almost never throw away my old notebooks. You never know what you will find there that might jog your memory.