tinydeer,
I think that I can discern tiny serrations on the margins of the leaves. If correct this would seem to exclude Ficus ,at least the ones that I am familiar with. Rather than try to post more pictures, try this, Google for images of Chinese Bird Plum and tell us what you think.
OK MY first bonsai blunders were to use pro-mix for trees in a pot. I drowned my little tree babies with too small particle soil. Good soil for a tree inna tray is pretty chunky. Also big-box stores carry cactus soil mix, which is a fair alternate for a single (or few) trees.
This is just me starting at the feet of your new tree.
This is just me starting at the feet of your new tree.