Hi Kirkus,
Sounds like you had a fun time trying to capture the ISS. It is definitely not for the faint hearted.
I get a real buzz when I watch an ISS passing.
I can still remember the first time I attempted to capture the ISS. I was set up ready for the passing. A minute passed and still no ISS. Luckily I spotted it rising in the opposite direction behind me. I had to pick up the scope and reposition it. The adrenalin really started to pump.
All in all, it is definitely a difficult task but as you get more and more comfortable following a small dot across that darts across the sky, I'm sure you will be able to capture the ISS.
Keep at it and good luck for next time.
What camera were you using?