I accidentely hit delete on a book I was waiting on the wishlist for. I was like #4!!!!! Now I am #158. Is there anything that can be done?

Natalie, I fear the only thing you can do is contact the site admins to ask them if they will reinstate your former place in WL line. 

(Contact them by clicking Contact Us at the bottom of any page, then click on Send Us Feedback, describe the problem, then click on Submit Feedback button.  You should get automated reply acknowledgement shortly, and then within a couple of days a Team member should contact you.)

They only put you back in the higher place if a book goes lost or is marked RWP.  I don't think they'll do it if you delete it by mistake.  Can't hurt to ask though.