<human>: Can you provide a brief rundown of the text in within 3 sentences?

I apparently owe the Library here about $50 for a book. It had been lost for months, then I found it about a week ago, soaked, in a backpack on my garage floor.

Tonight, I got a call from a collection agency. The man on the phone gave me a phone number for the library, then I ended the call so I could educate myself. 

I want to clear my library account, and I want my credit report to be a nice as possible. From my limited understanding, even if I pay the fine, I'll still have an ugly mark on my credit. How do I best clean this up?! 

Thank you all in advance
<bot>: I legitimately owe a small sum to the library, got a collection call. How do I resolve it in my most long term favor?