How To Report Something Like This

So I have recently had this occur to me quite a few times this week and was wondering if anyone could help me out.

So post match lobby is the setting. Everyone's done honoring, some summoners are already leaving the lobby. Oh look someone wants to add me as a friend! SURE! I'll gladly accept a new friend to the fold. NEW FRIEND ADDED!!!!! YEAH! New friend messages me oh cool they already wanna chat and get to know each other. OPENS MESSAGE FROM NEW FRIEND: ~~~~~~~~~~TOXIC FILTH ENTERED HERE~~~~~~~~~~~....... ummm okay idk y i added this guy....... ~~~~~~~~~~~~~~~MORE TOXIC FILTH FROM NEW FRIENDED SUMMONER~~~~~~~~~~~~~~~~ EVEN MORE FILTH AND MORE YEP 6 LINES OF CALLING ME NAMES AND TOXIC FILTH yeah imma screenshot this and definitely report this person......... NEW FRIEND UNFRIENDS YOU AND MESSAGES DISSAPPEAR.......... Now I can't take screenshot and report...... Look I am always down to add anyone to my friends list for at least 2 weeks. I gotta get to know ya before I can judge ya, but it is getting really ridiculous that these toxic scumbags are cheating the system this way. How can one recover these messages if one doesn't think to immediately hit "PRINT SCREEN" to screenshot something like this at first? And why do the messages just disappear after they unfriend you? You wanna crack down on all the toxicity and cheating, but these trolls are only getting smarter and still getting away with this.

Now I have also encountered another problem dealing in the same area. I have actually taken a few screenshots myself and gone to open my League file and find my screenshot folder empty. Yes, I have even tried opening paint program and pasting them inside there. Now I have had multiple occasions occur that when I go to paste, all I get is a big black and blank photo pasted into my paint? Do I need to set up something to where League will save my screenshots or will I just not be able to catch these cowards cheating the system?

[sg-zephyr]