Sure they know!! Their sense of smell is SO astute, trust me -- your dog knows what you had for dinner last night even if you didn't eat at home!!
True story -- back when we had Muffin the Intrepid (another Eng. cocker) and he had surgery to remove a cancerous tumor, I decided to start him with a vet who did acupuncture. Muffin was deaf (had both ears removed previously because of ongoing infections and some major mega long-term ear problems) and so I always went to great lengths to communicate with him, and I wanted him to know this wasn't going to hurt him.
I have been getting acupuncture for many years and I asked my acupuncturist if I could bring Muffin WITH me the next time I got treated. Dr. Shin said fine so he came in with me and watched as she needled me.
When she took the needles out, he came up and wanted strongly to 'sniff' them and I told her to let him. She held out a couple of needles and man -- he sniffed and SNIFFED and *****SNIFFED*****.
Then he just sat down and looked up at me. Dr. Shin just shook her head and said "WOW ... I wish *I* knew now about the 'inside' of you that HE now knows because of what he smelled on these needles!!"
It's true -- they *know* things by scent that we don't even know CAN be known.