Ask any real estate agent and they will tell you a similar sad story. The seller, whose home just hit the market, received an offer which was less than the list price, but felt secure their home would sell quickly and countered for more. For whatever reason, the buyer did not continue to negotiate and moved on.
For many people, their home is their largest asset and their best performing investment. The equity in a home is the difference in what it is worth and what is owed. Two dynamics, appreciation and unpaid balance, work in concert to make homeowner's equity grow.