That’s exactly what I saw only with scrolling lights on the whole side. Scared the heck out of me until it got close enough for me to see the lights were displaying scrolling text. Advertisement
I suspect what caused confusion is on that day the overcast sky was grey and it matched the color of the blimp causing the shape of the blimp to blend into the sky.
The result was the real shape of the blimp was obscured.
You can clearly see the moving text.
On a side note, why is it difficult for people to hold a camera steady?