I'm not sure if the messydos or other PC disk reading software you're using (crossdos) likes truncated names ... someting like schorche~1.lha ... Just for trying, rename the file on the PC and be sure that the base name (without the extension) is at maximum 8 charaters...
Then if possible, and the Amiga, copy it from drive to the HD or RAM and decompress it from there (I hav the impression that lha'ing from pc0: sometimes makes it wrong ... i know it doesn't makes much sense, but I make this faded memory ... maybe just a glitch

)
for formating the disk on the Amiga, i think you can do a format PC0: or on the workbench, select the drive (PC0: ?) and from the Icons menu, Format disk.
one more thing : if you format the disk on the PC as 720KB using a 1.44MB high density (are there still 720KB for sale ?!) be sure to cover the hole on the disk on the opposite side of the write-protection switch... Low density disks don't have that hole and the PC drive distinguises one from the other type by it.