Seeking strategies for negotiating Pre-Owed Car from Dealership by phone or online

Unfortunately my car was totaled last weekend, and I have to continue to work in another state. I'd like to buy from my hometown and only have time to come home on the weekends. Not my fault, but the other party doesn't have insurance, and I can't afford rental for much longer or have time to look for a car much longer. I'm the desperate party here.

I initiated contact on a car I really liked through phone today and told them I only had a budget of 19K and could they work with me, but was told that they priced aggressively and can only talk about price in person. They didn't even take my number or info, they just seemed uninterested. The advertised price was 20.5K and about average on KBB.

Any tips? Should I bother with online reps? I've only had experience negotiating in person. I will come home this Friday and go straight to the dealership. I was hoping of dropping some seeds today and getting the juice moving so it'll slow cook and be ready by Friday. Didn't expect them to be completely uninterested :(

Help please! Thanks!!