It could have been a palpatation or it could have been your stomach. Either way, if it is gone now you probably have no need to worry.
To be honest, I don't quite understand your symptoms.
I know it's extremely difficult to describe the sensations you can get in your chest during palpitations, especially the one caused by the short pause after a PAC / PVC. Some people describe it like a garden hose suddenly emptied, some describe it like the heart beats backwards. This "liquid" feeling is new to me, though.
I can feel the normal beat after a PAC as a "wave" going upward and downward, probably caused by a higher amound of blood pumped out.
There is a condition where you have liquid around your heart, named pericarditis, an inflammation in pericard, the membrane surrounding your heart. This can possibly cause liquid to gather between the membrane and your heart. Anyway, pericarditis would cause quite severe pain, and severe symptoms if your heart beats are prevented/reduced by excess liquid.
My guess is that you have palpitations (PACs, PVCs or tachycardia) and the symptoms feel weird. Anyway, you should see a doctor just to get a professional opinion on this. If no murmurs are present, this is probably benign. An alternative is trying to describe this phenomenon slightly more detailed. I would recommend seeing a doctor, though.