This is the so-called "adversarial passive".
I give a detailed explanation of passives (including the "adversarial" ones) here:
> object marker in this {} sentence
In your case:
⇓ **Active Sentence** : ⇓
⇓ **Passive Sentence** : ⇓
That is to say, gets lifted to , and gets lifted to .
As mentioned in the other answer, when a -marked thing gets lifted to , it results in that thing ( in your case) being "affected", and in general that means "negatively affected".
If you were to lift to , like you suggested, it would be perfectly fine, but that sentence would lack the implications of
1. the letter being someone's (i.e., it would just be " **a** / **the** letter" as opposed to " **my** letter" or whoever the context suggests as the owner);
2. that someone being negatively affected by the seeing event.