It is always a good idea to get a puppy used to being left alone for periods of time.
After all we can't be there 24/7 for them.
I find the best way to do this is leave the puppy alone only for a short period at first then increasing the length of time it is left alone gradually.
I would probably start with 10 mins then increase this over time.
It also gives the puppy a chance to rest.
I don't know where your puppy sleeps but when your in bed the puppy will be alone.
Some puppies can be left straight away,others need a little more time.
I would never leave a young puppy for more than 2 hours and always make sure it has plenty of fresh drinking water.
I'm sure everthing will be ok, puppies are very adaptable.
Most pups need plenty of sleep so are fine .
You may have to clean up after him or her though when you return
So don't worry to much and enjoy your shopping trips.