Guild Wars 2

When upgrading our guild hall today, I bought something for 7700 influence in our guild.
Then suddenly the merchant disappeared, I cant remember what the item was.
After further investigation I noticed that nothing happened, so I was wondering what did I spend the influence on or is this some bug where I just wasted the influence? :/

My guild is looking to get a arena for tournaments, but I had some questions
1. When buying the arena is it built right away?
2. The first 30 days are free?
3. Do the rest of the days cost 2g?
4. Do you need to pay 2g every day to keep it alive?
5. Can you pay 4g+ to keep it working for 2+ days? (essentially paying in advance)
6. I heard rumors saying if you dont pay it in 2 weeks it disappears. (kinda refers to number 4) if this is true could I wait 13 days and then pay for it once? Then pay again in another 13 days? (hopefully that made sense)