If this is an asphalt driveway... The kind of damage that he is describing is certainly possible. The only questions I have is... How much is a little bit of Mineral Spirits? Usually when you go and ask and employee about something like this they ALWAYS downplay what actually happened.
Here is one possible way this type of damage can take place:
The mineral spirits has to penetrate into the driveway. It will then attack the 'liquid bitumen' (or 'mineral pitch' or 'brea' or 'asphalt cement') and soften it while lowering the viscosity. Other solvents that will attack asphalt are other organic solvents (like toluene, hexane, methylene chloride, Stoddard solvent), aqueous sodium hydroxide solutions (caustic), and hydrochloric acid solutions (like muriatic). If the top layer of asphalt 'recovers' it can hold the mineral spirits under the surface and keep it from evaporating. If this happens, the bitumen would become fairly liquid (depending on the amount of MS) and the bound rocks and agregate could become unbound. This could cause the asphalt to 'sink'.
Hope this works out for you...