Spike in water use

We just received our water bill and I was floored to see that it had gone up by $240! It basically states that we went from using 8 CCF to 24 CCF (a difference of nearly 12,000 GALLONS) in 3 months. I went outside and checked our meter and the meter read was right. I called the Water Bureau and they are sending someone out next week to double check.

I did the blue-dye in the toilet tank test to see if it was leaking (it wasn't) and checked our outside hoses, faucets, etc. and nothing appears to be leaking inside. I turned off the water inside and checked the leak indicator on the meter and it wasn't moving. I checked the yard where the pipes run from the street into the house and it wasn't damper than I would expect (we live in Portland, OR so it's usually a little wet but yesterday it was sunny and dry and so was the yard).

I would imagine that if we had a leak somewhere that increased our usage by 12,000 gallons it would be pretty noticable, right? As in, the yard and/or house would be flooding pretty bad? I can't imagine a small trickle would cause that much usage and not show any physical signs at some point.

So, HD, what am I missing? What else can I check? What else could it be? When we purchased the house, we had our lines scoped and the inspector noted that there was a pretty significant hole in the city-owned water line on the street. Could that have done something? I'll definitely talk with the WB more once they come back out but in the meantime I want to be proactive in case something is leaking so we aren't slapped with another huge bill in the summer.

TIA!

ETA: My wife checked the meter when she left for work this morning around 11 a.m. and I checked it when I got home around 4 p.m. so we could see if there was any change when no one was home for a few hours. It was exactly the same.