What will happen if you miss one day of not wearing the compression hose after having vein surgery 4-5 days ago?

I would not worry at all.  There is no consensus even among doctors as to how long they should be worn.Some recommend 3 days, some one week, some 2.

I instruct my patients to wear their compression stocking around the clock for 48 hours.  Then I tell them to wear it for the rest of the week (7 days total) only during the day when they are up and about.  You should be fine!Dr. C