And now for something completely random

Closing windows on my desktop, I was cleaning up two days worth of clutter. Beneath three Ecto layers I found a cryptic little poem. Did I write this? I sat frowning for a few seconds. Then my eyebrows lifted my face; I had written it last night, my mind replied, but I needed to string together what facts I could recall: I had put on heavy eyelids, a light shone down the hall, metered by snoring, the laptop was too warm on my lap. A car dealership ad jostled my thoughts, Forwards, backwards, backwards. I had written this in my sleep:

I’m stop an elderly gelding
White and mellow
He is standing on a tidal flat.

A poem? Or was I dreaming? Did a TV ad filter into mysubconscience?
Did something happen to Marshmellow, the grey gelding I sold in Point Reyes? I feel compelled to search for his owner and find out.

I just turned a year older while thinking this over in my mind.