linked docx file disappears from links window when text boxes are linked together

@david mcnicholas

Order of linking matters.

I've posted recently about something similar: 

https://community.adobe.com/t5/indesign-discussions/three-chapters-missing-from-toc/m-p/15278963#M621545

When you link TextFrame (A) to another TextFrame (B) - parent Story of the (B) is being "absorbed" by parent Story of (A) - and cease to exist - including any links of (B)'s parent Story.

Right took some testing to find out what you might have done. I can't replicate exactly what you did, and seem to have done the opposite trick, but still demonstrates what might be happening.

Looks like you have a Text Frame on Parent Page T

When you untether things from Parent Pages - they tend to retain all the settings until they are overridden by the user. Here, you're untethering the link by threading between frames. 

The original link is removed, because you cannot have 2 text docs inside the same text frame. 

This seems to be linked to a Word Doc - but the Frame is empty - you possibly deleted the text out of the text frame to have a blank frame - but the link remains. 

Here you see the Link icon on top 

But you have Text Frame on Page 1 that appears to be Unlinked

Possibly you saw it was a Linked doc file - but choose the Unlink option from the Links Panel

This makes it a normal Text Frame

Here you can see a similar setup to what you have the Top Frame no longer has a Link icon, however, it's still linked to the Parent Page which does have a Link icon still.

So this text frame is still promissed to the Parent Page text frame with the lInk attributes. 

When I link the bottom frame to the Top Frame it the Link disappears.

Because now the text is inserted to a text frame that was promissed to another link - basically you can't have 2 text docs in the same text frame - so it unlinks the text file so it can do what you need.