Loud arguing/ non registered guest

[Kristi1623]

I had guests in a second floor inform me that they left early because of late arriving, loud and Arguing guests on the floor below them. 

They didn’t out to me until after. 
How should I proceed, and approach the other guests, seeing as after we arrived to inspect nothing seemed out of the ordinary?

 The second floor guests we met personally and seemed like an very sweet young couple and they’re insistent that we’re not make them any offers!

[Anonymous]

@Kristi1623   I'm a little confused - the title of your post mentions a "non registered guest," but I can't tell how that factors into the situation. Did the guests on the lower floor happen to have visitors that you didn't approve at the time of the argument?