I can imagine how worried you were and it's so frustrating and scary when your leg gives out like that!
Interestingly, I had a similar strain that bothered me for quite some time.. that was when I was maybe 8 weeks post op. I need to go read over my recovery thread, but this is a good guess.
Then just lately I've been working out with light weights, etc. Now mind you, my right hip is almost 8 years post op but when doing the weighted ADDuction exercises and leg extensions, it flared up what I am thinking are the ligaments and or tendons in my hip again. It came right out of the blue!
I struggled not to fall down, too and was rather embarrassing when trying to do my tai chi class later the next week.
But this time I recovered fairly quickly and will continue to do the weight lifting but am going very carefully with the leg workouts. Gotta practice what we preach, right?
So I can just imagine how you struggled especially since you are still in the earlier months of your recovery.
Slow and steady wins the race, right? You will get there, please don't worry about the walking, it will get better, I'm wondering if you are walking where there's a slight incline or uneven ground? That can aggravate a new hip too.
BTW- the ER doctors put me on crutches too, for the first time. But didn't need them long and switched to two canes, then one. Time does heal.. I love that your surgeon was so attentive to you. That's wonderful.