Help! I Need Some Potty (advice)

Okay, emergency post here. Please, I beg of you. I really need your help!

Last Saturday we went to a picnic in the park. We went to the restrooms when we got there, and Sweetie sat down to go. But this toilet had a sensor flush. Well, she must have moved out of the sensor's way, so it flushed - very loudly - when she was still sitting on it.

Long story short - she freaked and refused to use the potty the whole time we were there, very grudgingly went at a store on our way home, and has since refused to go potty in any public restroom (even though each one we've been to since has been a regular toilet with a regular handle to flush yourself).

Tonight we went out to eat with her and wanted to go to Barnes & Noble afterwards. At the restaurant, she asked to go potty, but when Hubby took her - again, she freaked. She shakes, cries, grabs hold of us, tries to crawl out of the stall, etc., etc., etc.

I finally got her to go try again with me, telling her if she didn't go potty at the restaurant, we weren't going to the "train store" (B&N - because of the train in the kid's room). She went in with me, but again got really upset and didn't end up using the potty.

However, I was SOOOO looking forward to B&N that we thought we'd give her another shot anyway. We reminded her how she likes going potty at the Popcorn Store (the movie theater). We thought she could be very brave and pretend she was there instead. She said she thought she could do it, so we gave it a go. But Hubby took her immediately to the restroom, was with her in the bathroom for at least 5 minutes, and they came out unsuccessful. More shaking, crying and clinging to him.

We went right home. Me crying from frustration, stress and not getting to do something I was looking forward to. Sweetie just happy to be out of the "dreaded" potty room.

What's more, I don't think this whole weekend she's made it once to the potty at home without going a little in her underwear first. She knows better than this, tells us she'll try harder, but still, it continues.

We are so frustrated! We're on vacation this week and have lots of fun things planned. But we told her we can't go anywhere if she refuses to go potty in public places. No beach, no museum, no more restaurants or anything. Still, she always says she doesn't care - she won't go potty. So this route would most likely only end up punishing us, not her.

So I don't know what to do. The only solution I can think of is to take her little potty chair with us everywhere we go. But that's not really ideal. Or, I guess we could buy her some "magic" ear muffs to protect her from the loud noises.

I don't want to ruin our whole vacation over this, but she has got to get over her fear. Maybe severe consequences will do it???? I just don't know what to say to her to help her out or what to threaten her with that will matter enough to her to lose out on.

What are some of your suggestions, oh dear and mighty internet pals? Come on, help me out here! Am I going to the beach tomorrow or not? How can we fix this fear?

Thanks in advance. You're the best!