For local use with a hood the likelihood of losing a plug is about nil. OTOH, the probability of simply losing the things in the mess of packing up is high at first. I lost several pair and now use the red ones as they are easier to see/find. I'm also careful to put them away when I take them out, haven't lost any in over 5 years now.
If you are real paranoid about losing them these seem to work as well and are a bit more stable in the ear:
JBL Hydro Seals Vented Preformed Protective Earplugs Aqua Ear Plugs For Scuba and Free Diving
FWIW I've been using Proplugs for over 15 years (1000+ dives), cold water and tropical with no issues at all, and a distinct improvement in outer ear issues.
People that had problems with them either didn't fit them right (probably) or had no idea what they actually were for and how to use them properly, The probability of getting vertigo without them is
WAY higher than with them. Remember, you generally see complaints from people on line, far less likely to read happy stories.
(IMO the pitch that they help with clearing isn't valid. In my experience they don't affect clearing one way or the other, which is and entirely different issue than keeping water out of your ear).
You can (somewhat) protect a "scrubbed ear" with olive or mineral oil. Swimmer's ear in cold water is infrequent as the organisms (fungus usually) is not as adaptable to our body temperature. It is not uncommon in the tropics due to more similar temperatures and the high frequency of diving on vacation. If she got it from a pool, usually HIGHLY disinfected, she is susceptible indeed.