If you use a +survival item next time you rest using camping supplies, unless you change from the previous option selected, you still have access to the higher tier survival bonuses regardless of whether you still have + survival gear still equipped. This definitely works with +survival clothing, and I imagine it works with the plus survival scrolls too but I haven't tested them. Obviously there's a lot of scope for abuse here, as you can just use the +survival scroll and take a universally nice bonus (+movement speed/healing/damage against flanked/DR) permanently.

 

While this is a bug players can avoid trivially, such a deviation from how the mechanics are supposed to work seems a bit poor.

It looks like you get the bonus but you don't. And scrolls don't help anymore either.

I'm pretty sure that the survival bonus still shows as the higher level on your portrait, so do you mean even though it's showing the higher level bonus it's not implemented into any accuracy rolls? If so that's still quite misleading, even if the mechanics are working as intended and it is just a display issue.

I remember trying to obtain the flanking 3 bonus using scrolls and even though the game allowed me to select it (and later even without the scroll), I was finishing only with flanking 2 on my character's portrait. For the fun try to post a screen with a rogue having flanking 3 bonus without using +2 survival bonus from caed nua...