Do the obvious things like double checking the tracking - is there GPS? What does the tracking history show? - looking around your property, checking with neighbours etc.
If the tracking looks suspect, you could try Ebay Customer services to see what they advise.
Use the link below to get a callback. They open at 8am.
https://www.ebay.co.uk/help/eua?id=5275&mkevt=1&mkpid
"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)