Covering his tracks

Well yesterday was an eventful day alright.
The dogs get a quick walk around the corner before settling down for the night. Normal routine is that the husband takes them, as happened last night. Off to bed, bit book reading and then lights off and sleep. I was woken up by an odd noise but it soon went off and I was asleep again in no time. Awake again at 3:30am with the same sound so went down to investigate. Imagine my surprise when I found poor old Floyd outside the front door. Husband had only just shut him outside at last night!!! 
I was contemplating reporting him to the RSPCA.
Here he is wiping the paw prints off the front door. The noise I'd heard was Floyd jumping up and knocking the letterbox. Why didn't he just bark???