If the lady prefers that you leave it in an envelop and, as happened to me today, I realized I did not have an envelop as I was coming from work and forgot to grab one what do you do assuming you don't have the time to stop and buy a box of them? In short what do you do if you end up being a putz and find you are at her door and have no way to be discrete as she prefers?
You should always tell the gentleman what your preferences are in an email before the date. We are all different and have different expectations. Communication is key! Communicate what you expect, where, how you want the donation handled. Many want it placed in the bathroom, some want it slapped right down on the table. This can be confusing for the fellas, with everyones preferences being different. It's up to the individual provider to enlighten the men, and it's up to the men to be gentlemen and follow the providers wishes.