How does fungi appear out of nowhere?

I know that fungi can reproduce sexually and asexually in about six different ways, but what I know is that sexually or asexually there still has to be fungi for more fungi to grow either through budding or whatever. Fungi cannot just appear out of nowhere. Since this is true, why is that when you have excess water in the grouts of your bathroom sink fungi start appearing out of nowhere? Don't you need there to be fungi there originally? I mean how can they just grow out of water and thin air? I am so confused when it comes to this question as to where the Fungi is coming from? Please give suggestions. Thank You.

Probably because there's tiny spores in the air just floating around that you can't see, and when it lands in an ideal habitat it starts to grow and reproduce...

I just studied this, when conditions are hard, fungi reproduce sexually, then the spores have thick shells to withstand bad conditions, they float off, and they remain dormant until conditions are good, then they grow.

lol I am so knowledgable on this sugject...I know that sounds creepy but then again all us bio freaks do.
so anyways you a) need a moist warmer environment but that is not always the case its just most helpful and yes they are kind of like in thin air so to speak they travel like most diseases generally do (they are airborn spores) and once it reaches a moist warm environment at attaches itself to the area and begins to divide...and thats where they come from

tiny little spores are floating around in the air and when they find good conditions, they land, grow and reproduce.