Can a real estate company list your property through someone else that is buying your house but has yet to close on? The person I went to, to buy my home has not signed any closing papers with me and I believe legally the home is not his/her to sale yet. And since I have not signed closing papers and we are past the closing date listed on the contract I am no longer binded to the contract right. So isn't this some kind of violation or just normal practice with real estate agencies.
Usually, real estate companies will not list a property unless the person who lists the property owns it or has some other legal right such as a power of attorney to do so. Many contracts of sale contain a provision in which the seller warranties that the seller has marketable title to the property. Read your contract. You shoud also ask the real estate agent outright if the seller has title. It may be that the seller has a lien on the property the seller is trying to remove before the seller can close. There is not enough information in your question to tell but to answer your main question -- yes it is very unusal for a real estate company to list a property that is not owned by the persson listing the property.