What is "tsuchatta"? Is it "つちゃった" ? We don't have such Japanese. It maybe "っちゃった"(small 'tsu'＋'chatta'). If it is so, I can answer you. You wrote " the "chatta" at the end is a way of abbreviating "shimatta"". It's wrong. "shimatta" should be "teshimatta". ～て＋しまった（the past tense of しまう＝to finish） 会<あ>ってしまった→会っちゃった 立<た>ってしまった→立っちゃった 取<と>ってしまった→取っちゃった 行<い>ってしまった→行っちゃった

I'll answer to Jorge's comment to me. No. Your comprehension is wrong. The respondent doesn't say such a thing. 1. He wrote "..chatta/...te shimatta". But you wrote "the "chatta" at the end is a way of abbreviating "shimatta" ". Don't forget "te". 2. He didn't write " This "shimatta" is used not as the verb "shimau" but as the interjection which means "oops!" ". But you did it. This "chatta" is not the interjection which means "oops!" The interjection "chatta" is used by itself only or at the beginning of a sentence. 3. We can use "chatta" in none-accidental situation. この本<ほん>はもう読<よ>んじゃった。I've already read this book. 思い切って彼に告白しちゃった。I boldly confessed my love to him. 4. You wrote " "tsuchatta (つっちゃった)" is used to mean "oops! I said it!" or "oops! it slipped out!". " on the comment. Now I understand. But you should write " ttsucchatta (っつっちゃった)". Add "t" at the first and insert " c ". ～と言<い>ってしまった→ていっちゃった→つっちゃった　I've said "～" carelessly. You might talk about "なんつってっつっちゃった" in https://www.youtube.com/watch?v=yXcx0VYZ75E . 「なんつって」っつっちゃった。＝I said "なんつって(＝just kidding <a dialect>)”carelessly. I've heard "っつっちゃった" and the next expressions. なんつーか ／ (なんちゅうか)←なんとゆうか←何<なに>と言うか なんつったって←なんといったって←何と言ったとて I think these forms come from eastern Japan dialect. But "なんつって" is not popular. It's a dialect, even now. "なんちゃって＝just kidding" is used. So the speaker(ゆず子) is embarrassed.