Charles,

There’s another twist in the tale.

Turns out the recipient had opened the Word file in the laptop, not the android mobile.

I work at night, and the recipient was half-asleep when I asked whether she had opened the file in the mobile. She had said yes. Next morning she said she had opened another file in the mobile. The file where the styles had vanished, she had opened on the laptop.

I did get her to do as you had advised:

1) Save your document to the local hard drive, not open from email.

2) Start Word in safe mode. Open Office apps in safe mode on a Windows PC - Microsoft Office

3) Open the document from within Word using File > Open.

Of course, we started with a fresh copy of what I had sent earlier.

Yes, all the styles were there in safe mode.

Then she exited safe mode, and again opened the file in normal mode.

All the styles were still there.

I am not sure how the problem went away. Can opening Word is safe mode do some repairs?