Calling 911, Not What I Expected

So, this isn't really a random, crazy or brilliant thought more of a scary thought.
Alexis, our 5 year old has a cold and is all snuffly and stuffy, coughing and whining.
To make her feel better, I gave her a cold medicine tablet yesterday morning. Worked great so we went about our day.
Zachary, our 7 year old has problems sleeping and has been prescribed melatonin to help him relax every once and awhile.
So last night was one of those nights he just couldn't wind down and at 10:30pm, I decided to give him a does but I couldn't find it.
A voice inside to me to check Lexi's room, and when I went in, I discovered an empty pack of cold medicine and and empty pack of melatonin. So of course I freak out and try to wake her up. She was totally out of it but would wake up for a second, smile then her eyes would roll back and she would fall back asleep. I wasn't sure if it was a full blown emergency so I called Health Link. After a couple of minutes explaining what had happened, her supervisor told us to call 911 and transferred us over..... and this is the scary part!
After I was transferred, thinking to myself, I can't believe I am actually calling 911, a message came on saying that all operators were busy and to call back later. REALLY?!
Now, this is the first time that I have ever had to call 911 so not too familiar with the process but is it normal to get a busy signal when calling about an emergency? That just seems so wrong.
So after the busy signal, we tried getting her up and awake. After a couple of minutes, she was mostly alert and answering questions so we decided not to call back and kept an eye on her for the rest of the night.
I can definitely say that was one of the scariest moment of my life as a mom... and an even scarier moment knowing that when I needed to call 911, they were busy.
I'm not sure how she got a hold of the meds as they were in the cabinet above the sink but I guess now that the kids are getting older and can reach higher, it's time for all of that kind of stuff to get moved into a vault.
Lexi is fine this morning and back to her old self so I feel very lucky that we dodged a bullet but still so so so scary!