Had the same(ish) thing after I fitted a B+M quickshift.

I lost 2nd 4th and reverse, as if they had moved in the box, so I kinda just put it in 3rd, aimed for 4th amd pulled until it went.

It went.. and I was left with fuck all. Broken cable was a nightmare to replace.

Should have got a pic as its quite an impressive cable to break by hand!