With alertgate when Ian had about 50 million or something ridiculous alerts to move and he sensibly decided deleting them would be far easier, I thought I'd put my suggestions in blog format.
I realise this doesn't bring them back and isn't retrospectively helpful, but for the future at least you know special alerts / achievements can be accessed elsewhere should something else happen.
1) Screenshot your screen. There are several ways you can do this. There is a "prt sc" button on your keyboard that takes a screenshot of your current screen. You can also install add-ons to Chrome / Firefox (and probably IE but I don't use that craphole : ) ). Examples are shown here:
2) You can then then paste your into your picture editing software (I just use Paint in all honesty! ) and crop that around the alert / achievement if you have used the "prt sc" function or the screenshot addons often give you the opportunity to edit it there and then and then save it.
3) Create an imgur account. This gives you infinite upload space for your pictures and you can make them public or not, place them in albums and organise as you see fit. I REALLY like imgur and use it myself for signatures etc. You can get to imgur here: http://www.imgur.com
4) Upload to imgur. This is startlingly easy - you literally just drag and drop your saved picture onto imgur's page and it uploads. You can name it, write a description etc...
5) You can use imgur to embed in forums and blogs, so you can create your own memories in a blog on mara or just use your imgur account to browse and reminisce.
I hope this is useful to people and if you need any further information just let me know. I know how important things can be to folks and I feel this will be a good way for you to have a "backup" of important things for yourself.