How to recover a lost volume size of Flash memory?

I have got a 8 Gb flash mememory stick.
I tried to install a LINUX distro on it but it
did not work.

I plugged the stick in the XP computer.
In XP I saw two partitions on the stick. the second one, about 400 Mb, greyed out.
Then I stupidly deleted the second greyed out partition. A volumesize of 7,6 Gb was left.
I learned that XP can not handle two partitions on a flsah memeory stick so I changed the driver of the stick to handle two partitions. This wokrs fine but I am not able to recover the deleted volume size of 400Mb.

Whatever I do, Linux or Windows, they keep on reporting a device with 8 Gb but with a max volumesize of 7,6 Gb.

Does anyone know how can I recover the lost volumesize of 400Mb?

Thanks in advance.

gr. Adam