I wanted to explain in my OP, that the info provided was for the flash drive itself of possible issues/problems. I exclude anything related to the USB port. Items, such as dirty contacts, surge voltage, broken hub or USB port. This by its own failure can cause flash drive to fail as well or on next usage. Hope that clears this up. -----Willy
Here are 3 possible reasons for a flash drive failure:
1) static, known as ESD(electrical static discharge)
2) rough handling
3) improper dismounts
Any of the above can cause physical damage or corruption of data. Most flash drives are a small pcb with electronics(interface) and the memory(data storage). ESD or static damage can compromise the small "gas discharge diode" to help dissipate electrical surges from static or suppress them. However, it can take only so much repeated hits or is overcomed or has failed, thus open to the next hit.
Rough handling by it own terms suggest either dropping or tossing the flash drive around which can knock-off any of the SMC(surface mounted components) and make a failure or distress circuitry, thus physical damage.
Improper dismounts can cause incomplete R/W's during the accessing period and may compromise the FAT or file structure of data. In other words, it was still working and you pulled the plug.
Under what I've explained, you should consider any ext. flash drives as working or temporary storage of data. Its great to dump your work from the office and take home to work on to include schoolwork, but only for that day. The data shouldn't reside for extended periods w/o having stored elsewhere as back-up or simply yesterday's work, etc.. Any recovery s/w may work or not, depending on the above flash drive failure. It's not going to work if there is true physical damage like ESD or broken circuitry. Data corruption is possible to recover from but attempts to do so may increase the corruption if not done properly.
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Please post or add to sticky if possible. -----Willy