Where does my text go when I apply a new master?

[adrm]

I must be missing something.

(Not really experienced in DTP, but I have used applications like PagePlus without problems in the past)

 

This is just an example:

1. Set up a new document.
2. Create a simple facing spread master with flow going from the even page frame to the next
3. Place a sample .docx file inside the frame on the first document page and auto-flow the text onto multiple new pages. Everything looks good, so far.
4. Clone a new master, this one with 2 columns in each text frame
5. Apply new master with Replace option to all pages of the document
6. All the text vanishes.

I guess that's all right(?), but I'd assume the text still exists in a buffer, ready to be reflowed onto the pages again. But I can't figure out a way to do it.

(Earlier I tried inserting 2 new pages in the middle of the text and applying the new master to that. After linking in the new pages to the flow manually, everything worked as expected.)

A hint please?