Hopefully it won't get lost - but I would think it will get delayed - there are warnings from all shippers to expect delays in the coming days until the systems smooth out.
I saw this applies - data may be passed electronically - anyway the buyer is liable for any tax due so you should be OK?... from RM site:
"As you’re sending to an address outside the United Kingdom, you’ll need to add a bit more information about your items. This will appear on the customs documents and may be sent electronically to the customs authority in the destination country."