Could be some type of miner (leaf miner?), the description sounds just right, except... I've never seen them on a fruit, just on leaves, however, they may affect fruit, not sure. Have you checked out this possibility? They leave small, thin trails in their wake and usually the trails are lighter in color (having eaten out the chlorophyll in leaves if my information is correct).

and here's a picture of the culprit and or damage.
any more suggestions. thanks by the way.

Here is a link that might be useful: tomato trail pic