A PSP game couldn't be found on the disc

[LunaMoo]

Sounds like your brother SD card could be fake. Market is filled with counterfeit micro sd cards produced in china with very tiny size and modified chip that shows much larger available space.
In such case files will appear to be there, but will be filled with 00's or FF's depending on the chip, so it doesn't matter what you copy there, once something get's copied there, it's no longer a working file. Small portion of fake sd cards are usually real, you can check such sd cards with a software like "H2testw" or similar software, just google for it.