Sympathies OP. I have had a hideous day today too (am Head of Year 10). Rude, defiant little sods all day. Lost my temper at one madam who refused to go to her lesson because of 'issues' with another girl (which I never do anything about...bullshit), then refused to go to HOD classroom then refused to go to my office then refused to speak to her mother on the phone, my shameless attempt to get her to behave.
Also on Friday I had to deal with a VERY pornographic cartoon which was drawn in an art lesson, then chucked across the classroom, unfortunately for them the teacher saw the boy throw it. Turns out one boy drew it, 3 more annotated it and another threw it. Tis true they are obsessed with knobs.
Teacher was more pissed off that it wasn't a very good picture, said boys were clearly not making enough progress! We all laughed about it actually.
but the point is that teenage boys are willy obsessed, teenagers are hormonal unreasonable beings who are very self absorbed.
Speak your colleagues to support you at the start of the next lesson, if you or any pastoral staff/SLT/HOY whoever can find out who it is then some kind of restorative justice works well, cleaning up etc... parents should be informed obviously.
A little tip...I would get one of the chatty girls who know all the gossip to tell you, they are a mine of information...I have spies everywhere!!
And try not to take it too personally, they don't know the real you just 'teacher you'
Have a big 