A man who left his door unlocked as he partied it up in Bridlington only realised a burglar had snuck in and stolen his wallet the following morning.
Police say the wallet was stolen from the victim's Promenade property while he was on a night out.
The burglary took place between between 10pm on Friday July 22 and 12pm on Saturday July 23.
Detective Chief Inspector Tony Cockerill added: “Unfortunately, insecurities are like an open invitation for opportunist sneak-in burglars who only need a few seconds to grab property from your home.
"Please keep your home secure and keep the sneak thief out!”
It comes as Humberside Police today revealed 69 'sneak-in' burglaries took place across the force area during July.
Of those, 14 were in East Yorkshire, 11 in North East Lincolnshire, 12 in North Lincolnshire and 32 in Hull.
A police spokesman added: "The public can support the forces Summer Acquisitive Crime Campaign and prevent burglaries by adopting crime prevention advice on the Humberside Police Website, keeping doors and windows locked, getting property registered onto www.immobilise.com so it can be identified/returned if lost or stolen and by calling Humberside Police with information about criminality.
"The public should call the police if they see people acting suspiciously in their community, if there is a burglary in progress or if they have details about those involved in criminality.
"This can be done this using 999 in an emergency, 101 in a non-emergency or Crimestoppers anonymously on 0800 555 111."