Hi Adam, it would be good to see the file. FYI, when you change the Tag of an item, it should/will be in the takeoff, yet it will be under the new tag name and possibly category (if you changed it). The best way to find it is to use the search function at the top of the Takeoff/estimate/BOQ.
To filter or find items in an estimate or BOQ, follow these steps;
1. Click the Takeoff / BOQ button in the PlusDesignBuild toolbar
2. Type in part or all of the material, component or product name (if you type the entire name it must be an exact name match)
3. Click the Search button. This will open any folders/categories it might be inside and highlight the item in a green colour. Note this will also work for recipes in your BIM report.
Let me know if this doesn't work, or copy and paste the items not estimating into a new Sketchup file & upload the model here, mate.