Is there a way to eliminate the chance of repeating section RowID collisions in change events?

When I get a repeating section record passed in through a change event , the RowID will be converted to lower case.  Is there a way to retrieve the "unvandalized" RowID?  Simply comparing it to every existing RowID in the section, converted to lower case, significantly increases the chance of a collision resulting in the wrong record being returned.

Not easily. It's hard to calculate the probability of a collision, it should be vanishingly small, but we all know that a small chance doesn't mean it won't happen.  About the only thing you could do is detect when a collision will be possible at the point a row is created, and recreate it to get a new row id. I don't know if you can do that from a sheet worker, but you definitely can from the API. 

You could do that via sheet worker relatively easily, although as Aaron said the chance of a duplication is vanishingly small.