Other players will usually handwave your disconnection if it's brief or obviously caused by connection issues.
Also, you have a period of 15 minutes or so to log back into the game before you become vulnerable to robbery or being dragged around.
To head up you just use 'up' or 'go up'. Some rooms have hidden exits you may 'search' for.
You can ask all these questions in Game-Help, and I welcome you to do so, you will find a quick answer there.
That being said, my personal advice is that how you play it off is up to you, but maybe you were exhausted from your travels...?
As the using stairs. Without giving away too much, which direction do the stairs go? Try that.
We have a coded protection for people who just fall asleep that keeps them from being messed with by other players for a little bit of time.
As for moving about, you can use EXAMINE HERE to look at the verbs in a room, and SEARCH to see if there are any hidden exits and such in the room. Stairs will typically (but not always) be either (u) up or (d) down.
Welcome to the game!
Sometimes a description will have stairs but there won't be an actual 'up/down'. Sometimes exits are hidden (the help search file is a great file to review) and sometimes they're just there for for flavour text.