Sucks but ours have to stalled stalled up for it - going to be scary for sure! There's an abandoned property next to us with way too many potential projectiles for it to be safe to leave them outside.
The procedure here is to use the livestock crayon to write name, phone number, and address on, then they get a break away halter with contact information in a ziplock bag duct taped to the cheek piece. A girl I know puts ID bracelets around their pasterns, but I'd be too worried in case of an injury - what if they swelled up with that wrapped around them?
Microchip is a waste of time in that sort of situation - by the time someone gets a scanner to your horse, you'd be in trouble. Remember after Andrew, when you'd hear stories about people coming up to horse pastures with busted up fencing and loading up other people's horses in their trailers? Ugh.