I doubt it's grease seen as your description says it's gummy and sticky, literally looks like bubblegum to me, god knows how that would get there though.

Rest assured it isn't coolant, as I don't think coolant would gum up like this. It's been two months since you've opened your hood, so if you would've had a coolant leak long enough for anything to gum up, you probably wouldn't have an engine anymore either.

You can quite easily check the colour of whatever coolant your car uses just by searching on Google where your coolant reservoir is, and taking a peak inside. It can be useful to know the colors of all your car's fluids so you can quickly identify a leak and it's severity, for example having a windshield washer leak is quite inconsequential, however losing a bunch of coolant can damage your engine beyond repair, and they could be hard to distinguish if you didn't know.