Unexpectedly Teleported off horse into Minecart on Railway 25 blocks above me

While riding a horse, pressing "W" to ride forward, there was a minecart travelling on the rail directly above me. (Railway is 25 blocks above the road I was riding the horse on). Suddenly when the minecart passed directly above me, I found I was riding the mine cart instead of the horse. Instant teleport 25 blocks up.