Translation:We will lose the ticket and we will go home.
It's a course for English speakers learning Irish, not a course for Irish speakers learning English. So even though the course has Irish->English translations, it's probably better for reinforcing the Irish patterns to avoid the ellipsis in English.
Unless the literal translation gives "bad English" there's no benefit in using a different English language idiom in Irish->English translations - you're not being tested on your English.
But the languages don't correspond exactly in terms of their syntax, morphology, etc.; rachaimid conveys more information in a single word than English can. I get that the point of this question is to get the learner to recognize all the information (tense, person, etc.) contained in that word, but if the learner does, and then produces a form which still has the same sense in English, that should be sufficient. The fact that English has more acceptable forms (within or across dialects) to convey it should not be marked against the learner, for that doesn't benefit them either. And it goes both ways: all the different ways to convey "I can" in Irish, for example.
Is the purpose of the course to have a perfect grammatical analysis of Irish, or to associate natural Irish (not that everything in the course is, I gather) with what sounds natural in English? And would it be that hard to use the "Another possible answer" bubble to politely remind users of other possibilities?
Really though, my main issue is with consistency with certain (dialectal) forms accepted sometimes, and not others. I'm sure it's a result of the course leads applying fixes and addressing comments over the last year, but it definitely does not profit the learner. Hopefully 2.0 will sort that out.
I think the only way that you can get consistency is to focus on the "translate what it says, not what it means" literal translations. As soon as you allow idiomatic English translations, you will inevitably have inconsistency, because it's impossible to get them all in the system from the beginning.
Obviously this doesn't apply to literal translations that have strong idiomatic association (tá hata ag Pól needs to be "Paul has a hat" not "a hat is at Paul" or "there is a hat at Paul"), but there is no benefit to accepting "and go home" in this case, because it clearly isn't a better translation than "and we will go home", and it's not as if "and we will go home" is wrong or in any way unusual in this case.
So I agree that a more consistent approach would be better, I just think that the best way to achieve that consistency is to reject unnecessary idioms, and that has the additional benefit of reinforcing the Irish structures.
Note that we're not having this discussion about translations into Irish, even though the ability to express ourselves in Irish is what we're trying to achieve on this course.