[mbyron]

The short answer is: it's very hard to know.

Here's the rule: the relevant rule is not the force play slide rule, but rather the rule that says a runner must slide or avoid contact with a fielder who has the ball. It's not clear from your description that this rule applies to your case: at the moment of collision, the fielder did not have the ball or had not had it for long.

Also, the runner might have been trying to avoid a collision, but the throw took the catcher into his path. In that case, he has not violated the rule, and it's just what what we call a train wreck.

But if the fielder had the ball and the runner did not avoid contact and did not slide, then it would be a correct call. That's very hard to know without seeing the play.