typically, if you have a parts list and a photo or two to back it up, the claims adjuster will take a value estimate from a knowledgeable source (like your LBS). no need for receipts.
also, if you are living full-time in a household with homeowners' coverage, you needn't do anything special to qualify for coverage. you're good.
i own a home, and a whole pile of expensive bikes. my wife had to get a rider for her jewelry (ie: extra cost for special high-value item coverage), which made me wonder about my bikes. so i called my agent...
'we had to get a rider for the jewelry. what about my bikes?'
'how much are we talking about?'
'$15k?'
'bicycles, with pedals?'
'yes.'
'wow. let me check...'
after looking into it, the official answer (at least as far as state farm is concerned) is as i said previously. bikes are covered. so long as you have some form of documentation regarding the make/model parts (a photo is fine) and a statement from a shop as to the value, they are covered. no limit to the coverage, no rider necessary.
but please, do your own due diligence. ymmv.