Just some random thoughts, I may be on the wrong track so let me know.
Does he steal stuff from other rooms or just the kitchen?
Does he have the opportunity to steal from other rooms, or is he never left anywhere else unattended?
Does he get alot of attention for doing this, eg you chasing after him trying to retrive the article? (Perfectly understandable if it is your phone btw).
Labradoodles are a cross between two very intellegent working breed and hence can be very clever and devious about getting attention.
It may help to give him a 'key', which is a toy that he has never played with before, but something you think will float his boat, you keep it in you possession for a while and produce it a few times, each time having a very enthusiastic game. Once he learns that that particular toy = a fun game with you, you leave it in his possession, then here is the slightly tricky bit, as I know you have a 6mo, every time he presents you with the toy, play with him, even if only for a few minutes, this way he has a sure fire way to get your attention and no longer needs to steal.
However, this won't work with food as it is too much of a temptation and he is not stealing it for attention but because he want to eat it.
Also it will only work if you always respond when presented with the toy, even if you are on the phone, changing a nappy, having a row......(that was when our old dog always used to present his key, maybe because he was stressed). But it does become a very useful communication tool for your dog.