That happened to me as well, I was paranoid about taking one home as a hitchhiker. After our Camino we spent a few days at Finisterre in a lovely apartment, with lovely crisp cotton sheets, relaxing after our walk.
I was severely bitten. The next day I realised I had lines of bites everywhere (except my face thankfully), although all up the back of my neck. On my feet, legs, arms, body, backs of my hands - even my toes. We checked the sheets, and they were spotted all over with blood. The blood spots were spread over a metre! I was literally covered in red spots.
Because I relaxed and used their sheets without thinking. Never again.
Tried to explain to the management , unsuccessfully, sealed the room up and nuked everything in a hot drier.
I do the same as you and have every thing in zipped bags, plus I had sprayed my pack thoroughly - and it was metres away from the bed.
Rang my husband to meet me at the airport with a large black plastic bin liner.
Thankfully that worked. Its not the bites that bother me so much, its bringing the things along with me.
I seriously dont want those critters in my house.