If you were an engineer from 2117 transported back in time by 100 years (the conceit - just assume this) and decided to get rich here in 2017 by taking the largest breakthrough you can think of from your time which is surely subject to patent protection and can surely work with the mechanics and technology of today, and is simple enough that you are 100.00% sure that you fully understand the mechanics of it and cannot possibly make any mistake, and, further, gives obvious utility so that it's basically impossible to get wrong and market incorrectly, then you would have a 0% chance of raising money and bringing it to market as a startup within 1 year. This is extremely certain. Nobody will give you the money to build your prototype, no matter what you say or show, as though every VC you spoke with were cursed with an inability to engage in abstract thinking or as if it were impossible to find a single VC anywhere in the world who can apply high-school level of physics. Your experience would be as though everyone you spoke with, while they spoke with you, had an 80-point drop in their IQ.
Under these conditions the real invisible unicorns are the ones that simply fail to climb out of this hole: they are the billion-dollar companies that are totally unfundable and simply do not make it past that stage and die.
Here is a Quora link to one of the best ideas I've ever heard in my life and easily the basis for building a $50B+ company. I ran across it as a VC quoted it as something like the "dumbest pitch they ever heard."
https://www.quora.com/What-are-the-best-horror-stories-about...
Actually the exact words were: "the most breathtakingly clueless company I have ever had pitch me (and I am not making this up.)"
This company was seeking $2 million only and clearly outlined a very specific growth plan. It is very easy to see the author's reasoning and the clear path they had for $50B+ as well as the likely reactions of other market participants.
If you are a founder of an invisible unicorn, it is important for you to not subject yourself to this ridicule. Not only will VC's waste your time and drive your company into the ground: they will gloat about it on Quora. The correct approach is to completely ignore them and be and stay invisible.
The seed-stage funding climate is completely broken and lots of great companies and ideas die for this reason; a few manage not to die somehow, as we hear about here.
For every invisible unicorn, there are a lot of premature unicorn deaths.
(Actually for this reason the word "incubator" is an excellent one, as it really is like an incubator of a premature birth of a youngling that will die if exposed to the elements and without intensive care and treatment.)