Jane, This time of year lots of hedges have been cut - so your dog might have picked up something sharp on her pads - and it might have fallen off later when getting a well earned lift home. Some of the thorns off the hedge clippings have punctured my tyres.
Spent years trailing around obedience shows with my parents. And working trials. l remember my mum working with one of her rotts - and the trail had been left some hours earlier but the wind and rain had blown the scent off course. The dog followed the scent well - but knew she had to find 3 articles that had been left - as they were well off the original course - she decided to just pick up random objects to make up for the missing ones.
Mum used to do obedience displays at village shows etc. One thing she did was get her dogs to retrieve eggs - without breaking them. Mine retrieve eggs from the hens and ducks - but only to eat. They will pick up - very gently - injured pheasants/pigeons/and rabbits with myxy - and bring them to me ‘to make better’. lts times like this l wish they would just quickly despatch them as l can’t.