structure of 忘れちゃうといけないからメモしといたのにそのメモをなくしちゃった。

Question

I try to figure out the structure of this sentence. but I'm somehow confuse with it

what I got is this

忘れちゃうと　いけないから、　in order to not forget

メモしといたのに　although noted it already

そのメモをなくしちゃった　that note is gone (lost it)

(If I got it right) it seem make sense to me but in grammar first two sentence is strange.

is it like this? ... although I noted it already (in order not to forget) but I lost it.

Answer 1

I try to figure out the structure of this sentence. but I'm somehow confuse with it

〔〈（忘れちゃう）と、いけない〉から、メモしといた〕のに、そのメモをなくしちゃった

is it like this? ...although I noted it already (in order not to forget) but I lost it.

Correct.

this type of encapsulation is quite new to me. (at least when it's in Japanese context, everything become new to me.

Here is the trick: when you interpret a Japanese sentence, just need to read it in inverse order.

I lost the note, although 〔I took it because〈 it was not good if（I forgot it）〉〕

I believe @snailboat can explain more about the grammatical phenomenon.