Be confident in yourself and you should be ok.
The worse that can happen is he say please do not come to my work,call me or maybe he say I am w/someone and coming here is awkward.
Don't be rude, but most importantly don't give him/her false hope.
I would advise against it. Never a good idea to visit someone at work- they could be busy and not able to talk. Not only that, it's just awkward, especially since you haven't seen them in three months or talked to them. There is a reason for that. Send a casual email first and see how that goes over.
Okay... but...... during those three months, how often did he contact you and say "Hey. How are you doing. Lets get together"? You wouldn't be asking his permission, just play it casual like "haven't seen you for a while, just wondering how you're doing. Let me know if you would like to get together for coffee or a drink sometime". Put the ball in his court and see how he responds to that before creating a potentially awkward situation.
Use your head on this. Work is not a good place for visiting someone for casual reasons. Again, when was the last time he tried contacting you?Don't appear needy. Or, shoot him the email and say something like " I'm going to be up in your area on _____. What time do you take lunch.? Want to get together"?
Because it's just not cool to drop by somewhere unannounced, especially if you haven't heard from him in months. What if he hasn't tried contacting you because he's not interested in a friendship? Why put yourself through that? Send an email first. Ask him how he's doing. If he makes no attempt at asking you to get together, than it's probably not a good idea just to drop by.
Omg. Are you really that blind? Not trying to be mean or out of line, but think about what you are saying! Fine, you didn't see him because he wasn't teaching, but, if he was interested in anything outside of the classroom, he would have made an attempt to see you! "Feel free to email anytime" means just that- no mention of getting together as friends or anything of that nature or having you stop by work. People email back and forth all the time. Facebook? Come on! Seems like this friendship is online only and one sided. You seem like a nice, sweet person. Don't let yourself be fooled.
That's scary. A talk in a very public place is in order.
Ok. Are you female? Because its a very different story if you're female..
It just is. I think you may be OK. Just don't blurt out the crush business.