Or stomach, or backside, or whatever, I know. I understand traveling is moving the foot or feet beyond the prescribed limits, and there is no pivot foot established in this case. But the case play deals specifically with gathering a loose ball and momentum causing the slide, or, iow, rewarding a good hustle play by not calling a violation on the slide. However, any attempt to roll over after the slide would be a travel, even though there is still no pivot foot established. Why is that? (I know, because the rule says so, but why does it say so?) I would say it is because the committee considers the rollover to be a "controlled movement", meant to circumvent the rule as written, vs. simple momentum from the slide. There are other examples of this distinction in the rules, for example setting the ball down, standing up, then picking the ball up - perfectly legal under the traveling rules, so they had to put in this exception. Momentum vs. "controlled" is also mentioned in going OOB - saving a ball from going OOB, or going OOB after attempting a layup are ok, but purposely going OOB to avoid a screen, for example, are not.

As I pictured the OP, the player had control the whole time, first by dribble, then by holding, while attempting a Fred Astaire/Curly Neal-type slide on the knees. To me, that seems to circumvent the traveling rules. However, if the ball was loose at any time, and fall to the knees was part of the attempt to recover, then I got nuthin'.

It's the sequence of events that makes it not a travel.
1. dribbling
2. falls to knees while still dribbling
3. slides on knees
4. picks up dribble WHILE sliding on knees

BUT, if he:
1. dribbling
2. falls to knees while still dribbling
3. picks up dribble THEN slides on knees
he is traveling.