Lost product when linking to multiple categories

I searched the FAQs and messages for this, if someone else has asked about it I missed it. :(

I was linking several items to a new category tonight, using the multiple link manager, when I got a message saying "I WOULD NOT ADD" and the product disappeared from the category it was originally assigned to. The product is still there because it shows up on a low-stock report, but I couldn't get it assigned to any category so it doesn't show up anywhere to be edited. When it happened again, I went straight to "edit the product" but couldn't fix the category-35 error.

How can I get these two products hooked back to categories?

Could you look in the table products_to_categories via phpMyAdmin and check if there is a reference to this Product's products_id in the table?

If not, you can add a row and insert the products_id and the categories_id where this Product should be located ...

Then, check if it shows in your Zen Cart Admin and edit the Product and make sure there is a master_categories_id set for it ...

As to the cause, I have never seen a Product lose all Categories from the products_to_categories using the Multiple Linked Products Manager ...