Looking on the internet deeply has found these results:

lost my train of thought is the most popular phrase on the web.

lost my chain of thought 14,560 results on the web	lost my train of thought 1216,000 results on the web More popular!
Some examples and use cases from the internet:	Some examples and use cases from the internet:
And yes, I have indeed lost my train of thought. Forgive me, I seem to have lost my train of thought. I can't protect you outside of my chain of command. You're breaking my chain of command. If it eases your mind any, you not being in my chain of command mitigates the impropriety. I'm sorry, I lost my train of thought. I just lost my train of thought. And speaking of losers, I lost my train of thought.	I'm sorry, I lost my train of thought. I just lost my train of thought. And yes, I have indeed lost my train of thought. And... totally lost my train of thought. Now I may have lost my train of thought several minutes ago, but if I continue to talk like this, no one will notice, and when I stop, you will applaud my energy. Forgive me, I seem to have lost my train of thought. And speaking of losers, I lost my train of thought. I seem to have lost my train of thought now.

lost my chain of thought

14,560 results on the web

lost my train of thought

1216,000 results on the web

More popular!

And yes, I have indeed lost my train of thought.
Forgive me, I seem to have lost my train of thought.
I can't protect you outside of my chain of command.
You're breaking my chain of command.
If it eases your mind any, you not being in my chain of command mitigates the impropriety.
I'm sorry, I lost my train of thought.
I just lost my train of thought.
And speaking of losers, I lost my train of thought.

I'm sorry, I lost my train of thought.
I just lost my train of thought.
And yes, I have indeed lost my train of thought.
And... totally lost my train of thought.
Now I may have lost my train of thought several minutes ago, but if I continue to talk like this, no one will notice, and when I stop, you will applaud my energy.
Forgive me, I seem to have lost my train of thought.
And speaking of losers, I lost my train of thought.
I seem to have lost my train of thought now.