I don't have an Id, but surely you should be;
1. Copying the files from the Lexar to the Id file system. Removing the Lexar.
2. Importing those files on the Id into MC on the Id.
Finish.
Or are you using the Lexar as your permanent store for files used on the Id? In which case;
1. Insert the Lexar into the Id and mount it if required.
2. Importing the files on the Lexar into MC on the Id. Leave the Lexar in place. Always, unless you have the setting "Fix broken Links" set to "Yes (protect files on missing drives)
Finish.
Regardless, if you are using the Sync Handheld function, it must be for some reason other than getting files onto the Id.
If you are trying to use the Sync Handheld function to get files into a MC installation on the Id, you are doing it wrong. I would expect that to break the process, and possibly delete files from the Lexar.