I've looked into this and it seems they are multiple ways with multiple nuances of saying "if (A) would have happened, then (B) would have happened. (third conditional ?)
My question is about:
To give context, it is a group of kids who share the responsability/usage of a single wallet, like their parents entrusted them with it. One kid who was holding on to it lost it. Then one of the other kids, says the following in words of comfort :
Anyone who would have had it/hold on to it would have lost it. For sure
That would be my english translation.
My meaning assumption with the nuances I understand : Even if it would have been someone else who had it, he would have lost it anyway. For sure.
I'm sure these translation/meaning assumption should be pretty close to it, but i'm very interested in your understanding/translation of this.
Now for the grammar I understand:
誰が= who, someone, anyone (why not 誰かが ?)
持ってても --> ていた (て form) + も = reverse condition = "even if" in that sentence, which creates the conditional form
失くしてた --> ていた = ている use for expressing state, or state as a result of actions in that case. = had lost it, I assume you get the meaning of "would" from the first part of the phrase, (like the も implies condition for both parts ?) Or at least that is my understanding from Tofugu Or is it something else that makes it a "would have" conditional verb ?
んだよ = のですよ = emphasis/explanation
My question is about 失くしてた : first of all why not 失くした and what different meaning it would imply ? What is the exact grammar point/ meaning for ていた in that case since Tofugu explains it only briefly? And what makes it a conditional phrase since this is a transitive verb ?
Also why 誰が and not 誰かが for saying anyone/anyone of us ?
Overall, is my understanding of the grammar points right ?
Have a great day
Edit : After reading stuff for 4 hours, I came upon this post which comes close to my understanding of this, but unfortunately not very detailed :
"However, if such sentence were about someone else and hypothetical meaning was possible, then the use of ている is preferred with both verbs similar to how we use past tense in English to make it counterfactual."
What I understood from all my reading is :
This sentence uses the Third Conditional form which needs ている to be applied on both clauses.
て form + も in the verb of the first clause indicates conditional
The third conditional in english always uses counterfactual sentences (see here, I don't know if that is the case in japanese ?
If anyone had adademic ressources or personal input for japanese third conditional (or counterfactual past conditional) that would be great !