Most employers that expect you to fill out paperwork, take tests, etc. will build that into the interview schedule. He expected your paperwork and tests to begin at the time he asked you to arrive.
You need to recognize the following as take-aways from this incident:
1) You should get rid of the pride to a reasonable extent. Don't be afraid to ask questions or cut the interviewer a bit of slack.
An acceptable period of time to wait for an interviewer where paperwork and tests are involved is 45-60 minutes. The interviewer isn't snubbing you by making you wait, he's simply scheduled other tasks to be completed while you're testing. If it seems like things are taking too long, you need to ask why.
B) Don't burn bridges that haven't even been finished.
This interviewer has likely labeled you as a flake, and with good reason. You flaked out in the middle of his process. Did he document and communicate the process properly? Maybe not -- but you admitted that you didn't ask. If you don't want people to flake out on you, don't flake out on them.
III) You are not special. You're not a beautiful and unique snowflake.
Your email reply to his "Where are you?" message betrayed more than a bit of self-importance. It betrayed that you believed your time to be more precious than his; that you believed your presumption of how the interview should go to be more important than the process that he set up and expected candidates to follow; that he was snubbing you by not greeting you or personally explaining the way he wanted to conduct the interview.
Let's look at Point III another way:
- He gave you a dedicated and substantial period of time to fill out paperwork and take his tests.
- He tasked his admin with assisting you in this process.
- He trusted his admin to represent his company by greeting you and taking care of you while he wrapped up other tasks.
You, an unemployed tech worker, are no more special than this business owner. He's recognized this on some level, as he's trusted his admin with some stuff that's pretty important to his business. He might have trusted you to take care of some stuff that's important to his business if you had stuck around a bit longer. He may not be that great a guy, or he could be the greatest man to walk this earth -- who knows? -- but he's doing something right, seeing as he's making enough money to pay a few people pretty well.
He also told you off in a diplomatic manner after you showed your ass. Maybe you should emulate his example.