[ansible]

It may have made a new filesystem and written that to your NAND Flash or eMMC drive partition. So the filesystem itself won't contain any old data.

Depending on the type of filesystem used, it may have walked through all the blocks of the NAND Flash, erased them, and then marked them as 'ready for use'.

If you are very serious about this, your best bet is to (A) stop using the phone now, (B) dump the raw partition contents using the Android tools.

The situation might be better or worse if the phone uses eMMC, but the above holds. The chip itself does the Flash management (wear leveling, bad block detection, etc.). So it can hide more, but there may be leftover data from the old /data partition still in the unused blocks.

[graemian]

I'd love to know if the partition was completely wiped as you describe. It's a Galaxy S2 running Android 4.0.4. It's the /data partition on the internal storage, I think.

How would I find out?