You are not the first to travel down this road. Very simply, you didn't act quick enough to get on the inside track. Cash buyers almost always have an edge on buyers that need to finance. Having a cash buyer removes the uncertainty that is associated with a financed one. Too many sellers have been "burned" by going to contract, essentially taking their property off the market for an extended periiod of time, only to find out that their mortgage was denied.
The reason the seller's agent didn't respond to you may have been because they all ready had multiple offers on the table that included cash offers.
Today's market is a competitive one....buyers that win on landing great opportunities do so because they, understand the local market, know the buying process, and are prepared to act quickly when an opportunity presents itself.
It is disappointing to lose out on a home that seemed right for you but understand that each of these experiences brings you closer to the one that will meet with success. Keep trying....
Should they be communicating more, absolutely. Unfortunately, the industry as a whole seems to have an issue with timely follow-up.