Living together and being engaged does not give you any legal status to claim anything.
If you assisted him in the business by working for it without pay then you can argue that you have what is called a beneficial interest something which is not on paper but that you have earnt by helping
The issue would then arise as to what your interest is worth usually a percentage and if he is in debt how is it going to be paid.
If he declares bankruptcy his financial affairs are placed in the hands of a receiver whose job is to call in all his assets to use to pay creditors. Should the receiver find out about the phones then they will demand those too.
You need to use this information when it does you the most good. If he knows you know he will simply move them!