You need to follow the instructions under section 2. The file you create in this step is for implanting SolidModel IDs into so you can test them in Studio to try and find your lost union.
You shouldn’t be opening the corrupted union; it’s gone and you need to find the last good version of it (a SolidModel asset) uploaded to your account. That’s what this tutorial helps you do.
This worked, but I only found 1 union, how can I found the others unions?
If you chose a limit of 10 or greater for the API call and you only received 1 result, unfortunately the rest of your unions are likely unrecoverable, or may have been created by other users if you’re using Team Create. I’m not sure how this behaves with group games either, you may need to specify the groupID if this is a group game.
This. Is. AMAZING!
I never knew it was possible to recover corrupted unions!
This is SOOO useful!
Thank you so much!
I do all of that I save and it has disappeared again…
There is currently a bug where new unions turn invisible immediately after you publish/save. You need to restart Studio to see them but otherwise it looks like they’re okay (don’t try to undo to fix it, this will actually break the union).
Superb guide, thank you! You helped me to retrieve my work after 2 hours of solid modelling.
Many thanks.
This is super helpful! Helped me save a lot of work.
Quick note to anyone having problems: If you see < null> < /null> where < url> should be just edit the text to look like the picture. I don’t know why this happens (even with new, uncorrupted unions) but changing that to what it should look like worked fine for me.
FWIW this is what the “Save this place to a file on your desktop” part of section 2 is for. Saving this file causes the union to upload, thus initializing this attribute on the instance correctly.
This is really helpful 
Note: This worked to find a union I lost 2 days ago, just forgot this was a thing and figured i’d have to redo it.
Love this so much.
Simplified step 2 by providing a stripped down template file. Hopefully people will get less hung up on this part.
Actually I just rewrote the entire tutorial to use a script so it’s not so tedious anymore.
Absolute godsend! Just recovered a few of my corrupt unions with the old method and worked like a charm! It was fun seeing some of my really old unions from way back when trying to find the one I needed. 
I have a question, would this method work with meshes too? I got some corrupted meshparts which are invisible but they have collision and have no transparency.
Meshes are only uploaded once and are not modified in Studio. Your files for MeshParts are external so there is no need for a recovery method. If your meshes are invisible, you probably just have inverted normals or they may have been moderated.
What do you mean by two lines? Please be more specific with It
Is It copying this entire thing?
Are these even lines? What lines? There Is no way to know where lines end and begin, what are the lines?
In the screenshot you can see I copy the large block of XML text, not including the next cursor string and the straight dividing line of hyphens. These are the top two lines of output for that block of output, you should not copy them.
Refer to the next screenshot of notepad, it shows you what you should be pasting into the file.
You copied the top two lines of text I wrote not to copy. Do not include the ---- line or the text above it.
