Hello! I thought this may be a good topic to write about since 1: I haven’t posted in FOREVER on the forums. 2: I’ve been dealing with this issue recently with Charlie. Long story short, Charlie has been developing a habit of urinating on my rug instead of his litter box. (Don’t worry, the habit is slowly going away so I’m not concerned) I decided to explain what I’ve been doing to get rid of the stain. (Without needing a steamer or anything like that). Ok! Here’s what I do:
~ Get hot water and pour it on the carpet. It soaks up the stain. You will need to do it a few times, but you may be lucky and only have to do it once. 
~ Get a room freshener. (Something that is ok to put on the floor). This will get rid of the odor for 2 reasons, 1: Your bunny room/ wherever you keep your rabbit and 2: Your rabbit won’t smell the odor, therefor he/she will less likely to urinate there again.
~ Finally, block the area for a little if possible.
I hope this helped! Thanks for reading! <3