As far as I know, there's no possibilities to get back your old settings config. Happens every once a while to me, and I have to re-do the binds/settings manually all over again.
If this happens frequently to you, you might want to go to C>Program Files x86 > Multi Theft Auto 1.5>MTA>config. Over there, save the "coreconfig" file somewhere else by copying, so that next time you can just paste that.