To translate into plain English:
A flash storage device (thumb drive, SSD drive, MicroSD card, etc.) consists of two parts: one or more storage chips, and a controller chip to coordinate things. Most of the time, when a drive fails, it's because of a problem with the controller chip: the data is still sitting there, but can't be accessed through normal means.
What the data recovery company did was open up the drive and bypass the controller chip, accessing the storage chips directly. When they did this, they were unable to get any data from them. Of the possible causes they listed, the likely ones are a voltage spike (static electricity can damage the chips, rendering them partly or completely unreadable), or hot/cold cycles causing either wires within the chips or the chips themselves to break. Cosmic rays and alpha particles usually cause problems with RAM, not flash, and the problems are temporary.
Data recovery may still be possible on a theoretical level, but it's going to cost far, far more. Instead of spending a few hundred dollars for a data recovery company, you'll be spending a few hundred thousand dollars or more for a university-level laboratory to disassemble the chips and read the memory cells directly -- and there's still no certainty that you'll recover anything.