The seller is not to blame here and, if you have opened a case for 'item not received' Ebay may find in the seller's favour.
Doorstep thefts are increasingly common and it is difficult to get any compensation when you are the victim.
Have you contacted the courier to complain?
The photo clearly shows an indoor location. Have you checked that none of your neighbours has taken your parcel in for safekeeping?
"There are two ways to be fooled. One is to believe what isn't true; the other is to refuse to believe what is true.”
Søren Kierkegaard, Danish philosopher (1813 - 1855)