Just a note: Uber's valuation was higher in 2015 than it is right now...

No inside info on Uber, but it is common for options at private companies to have strike prices considerably below reported valuations, which is proper (and adjudicated by a third party) considering the reported private valuations usually based on preferred shares that come with extra rights. That said, I dunno what year Uber switched to RSU’s, which would make this moot.

It was $40b at start of 2015 and was rumored to be at $50b mid 2015. It's $53b currently.

That said with dilution, it's likely 2015 share price is less than it is today.

What's the point of a value if you can't realize it in any way ?

Well Uber IPO'd this year in May, so given that he/she left in 2018, I would count the parent poster as unlucky if they forfeited those shares after leaving.

Did they forfeit them? Or had they vested and in anticipation of IPO likely exercised either all or nearly all of their options and then sold post-IPO?

Before the Susan fowler thing they had a rule that you had 30 days to exercise your options after you leave or separate as they called it. Since the company's value went up so much most people couldn't afford to pay the tax and because it was private you couldn't sell it (employee lock out is in November). Lots of people were handcuffed because of this, and I know a few that walked away. After the Susan Fowler thing they changed the option thing to like 7 years.

I think they moved to RSU's in mid 2015 or 16.

With 4 years of tenure they should have vested much of their stock, but I'm not sure when Uber started doing grants rather than options. If they had options they may not have had the cash to exercise.