No I didn't get any alert from Evernote about strange IPs logging into my account.
I'm not sure they offer this service, and even if they did, by the time a suspicious IP has logged in, its too late.
I'm annoyed that Electrum let another user log into my account while I was logged in. How can they let two computers log into one account at the same time??
Because wallets aren't "accounts" that need to be logged in to. Electrum is simply an interface to allow you to interact with your seed and private keys in a user friendly way. If someone else has a copy of your seed, then they can interact with it in the exact same way. It would be like if someone had stolen some sensitive documents from your Evernote, and you were asking "How can Microsoft Word let two computers view the same document at the same time?"
Wish that I just stuck with Coinbase and LocalBitcoin wallet. Been using those for years without any issues.
Your situation is exactly why you shouldn't use online wallets. Storing information online is not safe, as you have unfortunately just found out.
I'm curious how this hacker found me in the first place and what I can do to avoid him in the future.
Do you use the same email address for all your logins? Do you use the same email for Evernote and for crypto related activities? What about the same password? There are countless services which have experienced hacks and have leaked millions of user credentials.
I didn't realize how important those seed words were.
As pointed out above, Electrum gives explicit instructions not to store these online.