Sorrowful greetings traveller, I’m sorry that your bonsai isn’t looking too good now (I’m Tralfamadorian, so my view on time is different)
The Woody Dwarves would like me to fill you in that that plant appears to be/have been a Rhododendron... but the particular state makes specifics a tad more difficult...
It appears to be dead, currently... however I have a couple that lived in an ill-conceived frost prison for the winter.. they LOOKED like that.. but about 3 weeks ago, started to push flower buds... look close.. is your tree pushing new buds....
Tug those dead leaves off (If they TRY hard to stay on, leave ‘em..)then you’ll be able to see more clearly if you are pushing new growth...
How warm’s your garage?... any light in there? Decent airflow?
You’ve crossed the bend to a WONDERFUL specialized-horticultural “eden” built upon free exchange of knowledge and experience. I love it here, I’m glad you found us.
If there are no new buds pushing, bend some branches lightly.. you’ll be able to feel the live tissues... it MAY feel light and brittle.. if the buds aren’t there, and the branches feel brittle, my condolences, friend.
Don’t let it discourage you...
Keep on, if you want it... make it happen.
Pleasure to make your acquaintance.
Send me a PM if you have problems attaining/affording material... don’t want your interest to drop.