Your command was "rrgn41,1:/41.bin" so the BIN file will be written as '41.bin' to the path specified.
Provided your nuvi 68 is a RWFS device, that command will have written the BIN file to the device's [usually hidden] RWFS partition in its internal flash disc. To check if it's got that, go to the 'Diagnostics Page' by pressing the speed field on the main Map page then hold the centre of speedometer for a ~5 secs. Scroll down and if it has the entry 'RWFS Settings' select it and enable 'Show RWFS in Mass Storage'. You can then check if you have the bin file there as it will be now visible to a PC with the 68 also set to 'Mass Storage' in MTP Settings [selection above RWSF Settings in the menu list]. If the 41.bin file is there in RWFS but has zero bytes content, then your unit uses region 154 for nonvol so read the initial post carefully.
To write to the media card with such devices the path must be 2:/ not 1:/ as it is for earlier units.