Front end wobble after hitting a bump

I agree something is loose in the front end. I have antique cars and have had that problem. In each case I found a loose component. One was a tie rod end and the other was a drag link end. I fixed them and the problem went away. The death wobble is a scary thing to have happen! If you can't find it I would take it to a reliable shop and have them check it out. That may also have something to do with the wandering problem, a front end alignment may be needed.
Good Luck!