A sad tail

A few nights ago, Heidi got away from me outside. She wouldn't come when I called, even though I offered "cookies". I finally left a "cookie" on the front door mat and went in for a minute. I was beginning to panic. I went out the back door looking and calling her. I went back to the front door, opened it and she ran in. She was gone for about 5 minutes.
I noticed immediately that her tail was tucked under. It is never tucked under as she never feels any remorse or shame.
She couldn't settle down. She paced all over the living room and couldn't be still. She got on my lap and I tried to examine her, but she immediately jumped back down.
I heard nothing outside like she was yelping in pain or anything. She didn't whine or cry when she came back in.
Her movements didn't seem impaired at all. She continued to pace for the next 45 minutes until I decided to go to bed.
Bedtime is always a turmoil, because she doesn't want to. I was afraid tonight would be even more chaotic than usual.
Instead, she went quietly to bed and I didn't hear from her anymore that night.
Her tail has been down since then. Two days after, her tail went up for a couple of minutes as she barked and carried on because cars had the temerity to park in front of the neighbors house.
Her tail is no longer curled under, but it is still hanging down. I don't know what could have caused this. Can a tail be broken? I certainly hope her jaunty little appendage comes back soon.