I've experienced a stolen iphone. Fortunately, the phone was recovered within a few hours but it was a sobering experience. Yes, losing your travel details, tickets, etc is bad but it is two factor authentication that is the real problem.
But, I can access what I need from the cloud on a new phone?
I'm sure you believe this but are you REALLY sure you can access icloud if you had to borrow or buy a new device? Go try it on a friends phone. Generally for the apple environment you need either another trusted device or your phone number as 2FA to access your icloud account. I could use my husband's iphone as a trusted device and I also have his number set up for 2FA, but traveling alone would be a different matter. Using his phone I could use find my and lock my phone. Traveling with your ipad or laptop gives you another trusted device, but without them you could not do anything unless you have some other backup system in place. You need to set up someone at home as a backup 2FA or as a "recovery contact" or generate a 28 digit "recovery code" to keep somewhere safe. Note- I have not had success setting up a recovery contact- I can set one up but it doesn't actually work to get a code. So test anything you think you have set up.
Even though I could access my Apple email, I use gmail as my primary email- the one that has all the ticket info, backup 2FA for my accounts, etc. I could not access this. Ironically before the trip I was reviewing my accounts and realized I had an old work phone number listed on my google account. I was deleting/shifting and then the website froze up and I forgot to go back and finish. In the process my husbands phone number was no longer listed as 2FA, only the stolen phone :( But wait- I know I had my icloud email set up as a "recovery email" on google! Guess what, that does not mean 2FA on the fly- it is for when you contact google for help once you have depleted the obvious phone numbers for 2FA and then that help page says because of security it will be "3-5 business days"
So if I didn't get my phone back, what would I have done? The solution I came up with was to buy a new iphone and then I could at least access apple cloud, rebuild my apps, have google maps, etc. But this would work only because I had access to a trusted device. How to access my gmail to get to everything else including saved and changed passwords. I was going to have to contact my dog sitter. Tell her where to find my laptop, give her my password (thankfully I trust her fully). Get her to go into gmail to add my husband's phone number for 2FA. It would have worked eventually but what a mess. Upon returning and looking further I realized that google lets you download 10 "backup codes" that you can print/save to give alternate access.
The lesson? Don't be complacent, look carefully into the security settings of whatever your primary environment/services are. Google "how to access xxxxx without my phone" or "without verification" and make sure you understand what you can and cannot do. Then ACTUALLY TRY IT on someone else's device. Go to the library and use their computer or try a friends phone. And recheck before every trip- software providers are notorious for making operational changes.