Hermiones bag

Me and my partner were watching Deathly Hallows Part 2 and were at the part where Snape asks for a flask before he dies and Hermione instantly grabs the flask from her bag without using Accio? How does this work is it a non verbal spell or just a miss from production? She made a very good point of surely the flask isn’t just waiting at the top of her bag when she has used the extendable charm. Does anyone know?