They're night creatures, coming out to feed on their hosts at nighttime, which generally allows them to go unobserved. They typically suck blood for approximately 5 minutes after which they disappear back into their visco elastic memory foam topper or other bedding material, leaving their hosts with irritations of the skin, inflammation, and the desire to scratch.

 

One way to find out is to remove the mattress topper for a few days & see if the problem ceases. If it does, then you have your answer.