Has that really happened to you? Wow, I have not yet known bad luck.
Yup, it's one of the deaths that I will not forget.
Which is why I, when encountering a sleeping nymph, either: lock her in her room if possible, or kill her outright.
Locking her in won't stop her teleport...
Nymphs are semi-useful for removing cursed equipment, if it's a big problem.
I always BUC my stuff before using (either by altar, pet or monster use), unless it's use-it-or-die situations. After liches start to appear I don't use anything not altar checked. To avoid typing errors I put unchecked items inside BoH (normal bags for wands that make engravings vanish), and #adjust their ids out of commonly used command buttons (like T, t, W, w, P, p, R, r, i, a).
I also never put on a helm/amulet without using identify (I don't price ID anything other than scroll of identify), and only test rings in safe places with a pet I can handle.
And speaking of #adjust, I have my own system... I often #adjust commonly used items' IDs.
a - Stethoscope. So I can quickly apply it every turn.
c - [Magic] whistle. Stands for "
calling my pets"
d - Pickaxe, for
dig.
e - if I have an athame or Magicbane. For a quick
Ee.
i - Bag [of holding], for
inventory.
l - Leash, if no magic whistle.
p - Towel or blindfold, for a quick
Pp.
q - Main ammo or thrown weapon stack, for a quick
Qq.
s - Unicorn horn, for it is next to
apply.
u - lockpick/key/credit card, for
unlock.
w - Main melee weapon, for a quick
ww.
x - If I got an oilskin bag. Wands that vanish will go inside, and if I'm going near water without water walk or levitation, the BoH goes inside too.