Could ativan (lorazepam) cause short-term memory?

Yes: Lorazepam (Ativan) is a member of the benzodiazepine class of medications. These suppress certain brain chemicals which is intended to reduce anxiety. However, side effects may include short-term memory loss and sedation, among others. Speak with your prescribing physician as soon as possible.

Ativan: Memory impairment is reported in 0.01% to 0.1% & amnesia is reported in 1% to 10% of people taking Ativan. REF: https://www.drugs.com/sfx/lorazepam-side-effects.html