@Pat8450 what would be your purpose in saying anything more to them about it, especially when they are leaving? Presumably they got your message, and even if they didn't, obviously after they depart the incident cannot recur. As others have mentioned they may see your unannounced entrance into their private space as as much of a violation as you see their entrance into yours, so I would certainly drop it. All you can possibly accomplish by bringing it up again is to leave them with an even worse final impression of you, probably triggering a more negative review and possibly a report to Airbnb that could bring down your listing.
FWIW, Airbnb terms of service say "The Host retains the right to re-enter the Accommodation during your stay, to the extent: (i) it is reasonably necessary, (ii) permitted by your contract with the Host, and (iii) consistent with applicable law." "Reasonably necessary" is obviously open to interpretation, but I doubt that retrieiving a snack basket qualifies.