Yeah, hate to give you bad news but this guy is toast. Why Bonsai does not come with instructions is irresponsible. Bonsai are just like a new pet. Constant attention.
Because of the limited root mass Bonsai need watering pretty much every single day. Usually the entire pot gets immersed in water. When the roots are healthy they suck up all the water so that air gets back into the soil and there is no chance of rot.
This guy died. Roots died. You keep watering with no drainage and there will be fungus, mold that thrives with high moisture.
Really upsets me to see this. And believe me we see this all of the time on this site. People are always getting these, sometimes very expensive and very old Bonsai as gifts. No instructions, no species and 99% of the time they die. That is my own statistic. Just as if you left a new puppy behind with no food or water. Come back and it is dead.
Friends who give these for gifts should be Bonsai experts that at least know you expect the responsibility as well as welcoming the responsibility. They should give instructions. Pay for a class in Bonsai. Otherwise, shoot, a plant that has been created by man, has lived 5, 10, 50 or more years is destined to die in the hands of a newbie. Not fair to the newbie. Not at all! Nor the plant.
I am sorry. Kind of hard to tell what species it was, doesn't matter now.