Gottcha, more happy hidden events. Well that's brutal, lol.
Sounds like a good idea to spend most of actual cash before the month rolls over then. Not like me - saving for 6x Hyper-Wave Decoders to build on the 1st to avoid maintenance bill. Although I hoard every unresearched dependency item since day-1. Probably 2x Old Earth Labs worth of stuff for which I have not discovered a purpose yet so I'm good.
@Yirtimd2
I toggle ON every button in graphs, zoom in, and cross reference zonal with country activity. Base presence usually trumps all other peaks as related nearby shipping also raise activity. I send a CONVOY to scout the area: from the Balkans it detected a base in Norway, so pretty large spotting radius. It needs to stay anchored for 2 hours to be able to detect it (from my tests).
Even so I don't think it was enemy base in your case. Seems too early too sudden, unless somehow the base was there for some time with frequent supply missions and whatnot. PIGEON's radar should be able to detect flybys with its huge radar. The only real early-game antidote, followed by CONVOY for the base (infinite fuel basically).
In these forums I also read about some mining ships that linger beyond your radar, land for eternity, and rape your score silently... Sounds like one (or more) of those. I shot down only a couple (I think it was them) in 10 months so far. Never seen a landed one. Maybe just lucky.
Prioritize new bases for continental radar coverage (overcharged radar is a Godsend). After that you can turtle up and play slowly at your own pace. I only check Graphs once a month now but make sure to shoot down every ship my SHARK JETBIKEs can dogfight and survive. Geoscape gets easier at least.