Apparently I'm in a minority here, but I'll be blunt:
Guys are totally oblivious! I once came across an article someone had written on how girls flirt, and suddenly realized I've been hit on my whole life and never knew it.
I kid you not, I even told a girl once that "I don't like coffee". I know it's true (even to this day), but man alive it would've been sooo nice if a girl came right up and told me "I want to date you", or to even know that my feelings of being unwanted were completely unwarranted.
In this day and age, texting is perfectly fine. Fun fact: me and my fiancee met on here, and predominately communicated via text and PM. It wasn't until I wrote her a letter (well, email, so "digital" letter?) that we started really taking things further. I kinda sorta knew she was somewhat interested in me, but it wasn't until I came across one of her posts on here that said it that I felt like an idiot and took it further. Thankfully it worked!
Although since most don't agree on texting, how's this: send him a heartfelt email telling him how you feel. Instead of trying to constrain it to 140 characters, say anything and everything you desire about it. If you don't have his email, text him and ask for it, saying you want to share a picture with him. Then take a picture of something you think he'll like (nothing "suggestive" though, don't put that in his head this early on
) and send it his way. He might think its dumb, or not even bother to respond, but you'll at least have his email and can send that letter when you're ready.
For what it's worth, my own parents sent many letters to each other, hand-written, but email wasn't well-known publicly until after I was old enough to use it, decades after their marriage. In this day and age, hand-written letters are nice, but if time is of the essence, go for an email 