Nope... I don't find out unless it's by a public source of data open to the world.
If you register as an investor, for any particular company you can see the list of investors, e.g. here: https://seedrs.com/startups/203/investments (only works for logged in seedrs investors). When you choose to make an investment, you can choose to do so "anonymously", such that your name does not appear--that's what the FAQ is referring to. So Microcosm can likely find out who has invested (even if you are not registered with Seedrs, perhaps you have friends who are?) but you have no right to that information.
If you register as an investor, for any particular company you can see the list of investors, e.g. here: https://seedrs.com/startups/203/investments (only works for logged in seedrs investors). When you choose to make an investment, you can choose to do so "anonymously", such that your name does not appear--that's what the FAQ is referring to. So Microcosm can likely find out who has invested (even if you are not registered with Seedrs, perhaps you have friends who are?) but you have no right to that information.