I’m not supporting snorting Vyvanse, but that’s not how it works.

Lisdexamfetamine is an inactive prodrug that is converted in the body to dextroamphetamine, a pharmacologically active compound that is responsible for the drug’s activity.[113] After oral ingestion, lisdexamfetamine is broken down by enzymes in red blood cells to form L-lysine, a naturally occurring essential amino acid, and dextroamphetamine.[6] The half-life of this conversion is roughly 1 hour. The conversion of lisdexamfetamine to dextroamphetamine is not affected by gastrointestinal pH and is unlikely to be affected by alterations in normal gastrointestinal transit times.

Enzymes in your blood convert it to dextroamphetamine, has nothing to do with stomach acid.

https://en.wikipedia.org/wiki/Lisdexamfetamine