Ok so the bubbles bit was a bad joke
You could of lost water because the care overheated and it blew it out the pressure cap. If thats the case you wont find a leak because you don't have one. Try running the engine at idle until it heats up. Carefully watch the temp gauge and make sure as it get hot - usually between 90 and 100 if it shows on gauge - the radiator cooling fans should come on. You should see the temp start to fall on the gauge and then the fans will switch off again. If they don't you have found your problem. It is quite common for fans to not work. During the winter you might not have got the car hot enough to need the fans so they could have been faulty when you bought it. Then you have to find out why the fans don't work. Could be fuse or duff temp switch, both easy to prove. When the car warms up does the heater blow hot air?