I had an issue with coolant loss(no lost cap) but the tank was leaking. I bought the tank and cap for $38 shipped(thanks Amazon!).
Replaced both fairly quickly, topped up and it was fine. The way the hose was attached to the previous tank left me concerned as it wasn't all the way up male part of the tank and the clamp wasn't in a solid spot. Thinking back though the cap was more likely the cause but safer than sorry.
My ongoing issue is the brakes/rotors. I had them replaced 2k miles ago and they are WARPED(deposits) again. I drive like grandpa, no hard breaking. Wheels need balancing again too(stupid roads in NJ).