That's simply not true. I've stayed at PH, TI, and the Venetian over the last 3 years for conferences and personal travel, I pass on housekeeping the whole week, and there have been no security checks like you describe.
I use my imagination. The most likely answer is that there was a check and they haven't noticed because they were out and about.
On a balance of probabilities without hearing more on how they specifically verified it I will still assume the alternate hypothesis. Which is that someone on the internet is very sure about something and they are wrong.
It is not due to a lack of imagination. Or because I haven't heard some cool spy trick you have heard about. It's because I find it (in the absence of other information) the most likely explanation given a lifetime of observations about human nature.
C’mon.
These are the same people that started to not change linens or provide new clean towels unless you ask (or infrequently) for ‘environmental reasons’. (Aka profit margins)
And yes, back in the day it was normal for housekeeping to clean every occupied room every day, unless you told them not to. Unless you were in a roach motel or something.
It's all in the small print too which nobody reads (these hotels have legal advisors).
I don't understand why you would not want them to clean your room as it's included in the price.
Most hotels stock at least two rolls of toilet paper too. I’ve personally never run out of toilet paper this quickly.
Most hotels I've stayed at give you at least 2 or 3 rolls of TP, and while the soap bars they give you are small, they last more than a week, easy.
answering for myself, having been in too many hotel rooms in my lifetime:
it's easier to ask for towels and toiletries than deal with binding arbitration after having things stolen from your room. I can make my own bed.