Snatch Arrows allows catching and hurling back at the attacker only thrown weapons
When a foe makes what would have been a successful ranged attack roll with a thrown weapon against a creature that possesses the feat Snatch Arrows, the creature can—instead of either deflecting the thrown weapon harmlessly or harmlessly catching and keeping the thrown weapon—harmlessly catch the thrown weapon and immediately make a ranged attack with that thrown weapon against the foe that attacked the creature with it originally; this is not an action.
A thrown weapon is typically usually a melee weapon possessing a printed range increment, like a club or shortspear, although there are exclusively ranged thrown weapons like the javelin. Alternatively, a thrown weapon is any weapon that has been thrown yet was not designed to be thrown. (Ranged attacks made with these weapons—including improvised weapons—have but a 10 ft. range increment and the attacker suffers a −4 penalty on his attack roll). Thus a creature possessing the feat Snatch Arrows could catch and hurl back, were one chucked at him, a throwing axe or a clumsily tossed longsword.
However, arrows, blowgun darts, crosbow bolts, sling stones, sling bullets, and the like are specifically ammunition—projectiles used in projectile weapons and not thrown weapons. Ammunition launched from a projectile weapon can be either deflected harmlessly or harmlessly caught, but such ammunition can't be thrown back at the attacker. (Note that shuriken, although functioning in some cases like ammunition, remain thrown weapons.)
It's possible—although rare—for a desperate foe to use a piece of ammunition as an improvised weapon, and then it's possible—and even rarer—for a foe to make a ranged attack against the creature with the feat Snatch Arrows by throwing that ammunition at the creature! In this weird case that I've never had come up in my campaigns ever, this GM would totally allow the creature that possesses the feat Snatch Arrows to harmlessly catch the thrown improvised weapon and immediately make a ranged attack with that thrown piece of ammunition against the foe, albeit with the appropriate and significant penalties (i.e. typically suffering at least a −4 penalty on the attack roll but possibly instead a −8 penalty if the GM rules the penalty from also using an improvised weapon stacks with the previous penalty).