Can We Be Held Financially Responsible For A Run Away Teen?

Location: Iowa

My (43f) boyfriend's (35m) daughter (18f) walked away from our family three months before her 18th birthday and graduation. Now we're being contacted by the school about replacing the laptop she didn't return.

For the past year his daughter had been pulling away from the family, avoiding interaction and consistently spending time with her boyfriend and his family. Unbeknownst to us, his mother had told her she was welcome to move in with them if she was having trouble. The Monday after prom, she went to his house after school and never came back. We both tried talking to her, my boyfriend talked to the father and I met with the mother. Nothing was resolved, she refused to return and communication broke down when we pointed out she was a minor and the family was breaking the law by commiting custodial interference.

Fast forward to graduation and the school began emailing her and cc'ing us about end of year fines, fees and responsibilities in order to graduate. She replied all (we don't think she meant to) and told the admin she'd been "financially abandoned" by her family and was unable to pay these fees. (She does work and she'd known about the laptop repair fee since November and the graduation fees all year) I left communication with the school up to her father. He did nothing and we heard nothing more about it. We're not sure if her boyfriend's family covered it or they were waived.

Today we got an email from the school just to my boyfriend and I saying we needed to return her laptop, charger and bag asap. I'm going to handle it this time around and explain to them that she chose to leave home, her father chose for the sake of any future relationship to not involve the school or police to bring her home for the last 3 months of her minorhood and that we have no idea where she or the laptop are.

What am I walking into? Once I explain we don't have contact with her or know where the laptop is, can they sue us for the value of the laptop? I'm assuming she spun some tale that caused them to waive her fines and then walked with the laptop and plans to use it in college. Whether or not she figured on us being stuck with the replacement cost, I don't know. What I do know is any attempt to speak to her or her boyfriend's family will not be successful.

UPDATE: Just got off the phone with the vice principal and explained briefly the situation, that we have no idea where she or the laptop are. He took my last known phone number for her and said he'd reach out to her directly and if he doesn't hear back he'll reach out to the mother of the family who moved her in. He sounded shocked and while he didn't say what happened to her end of year fees/fines he implied heavily that the principal and counselor worked together to waive everything. I think he realizes she scammed the school and because she got away with it once, she now thinks she's going to get a free laptop at our/the school's expense. He said he'd let me know what happens. No mention of replacement value/fee was mentioned so hopefully this gets ironed out.