The heroes wave tricorders when searching for the body parts. Are they merely matching their GPS coordinates to previous orbital scans? If so, why are they failing, and two tricorders out of three lead their operators to the wrong spot?
It doesn't look like a "pinpoint" job to me, but rather one that would absolutely require the witnessed tricorder-waving on the spot before a beam-up would be possible. So the way I would have done it (assuming an "approaching" ion storm does not yet create a health hazard that categorically precludes transporting) would certainly be beaming down to each vague spot, waving the tricorder, uncovering the component, slapping a commbadge or other tag on it, and beaming up - component by component. A shuttle could be standing by to recover a stranded team; surface transportation would not be required.
OTOH, just overflying in a shuttle might have drawbacks: not enough proximity for accurate scans, greater risk of somebody far away spotting the activity, etc. And our heroes wouldn't know what to expect until after surveying the first site up close. So a combination of shuttle and ground work would be the way to go - which means the buggy becomes an allowed feature, even if not a required one. Which is all the excuse Picard needs.