Dubitable Stain That Was Lost

Hello! I wanted to ask a question regarding the inspections during the seven clean days when the cloth was lost. 1. A woman who was uncertain about a stain that was on her tissue, suspecting that it might be blood, but carelessly threw the tissue away, and it is not possible to ask about it. 2. A woman who was uncertain about a stain that was on her underwear but accidentally washed it before asking. In the above cases, do we rule leniently because it is a doubt, or should we rule stringently and make a new ’hefsek taharah’ (a period during which a woman makes sure she’s not bleeding)? Thank you very much.

Shalom!
If there is a doubt whether a stain is impure, and it is impossible to clarify this, as in these cases, one should be lenient.
This is only a general answer. In reality, when clarifying this question with the woman, it often turns out that in fact there wasn’t any doubt. Therefore, one should ask a Rabbi in each case individually.

Shulchan Aruch, Section Yoreh Deah, chapter