Keep calm, it is not possible anything could disappear on this site as nothing is in fact deleted. Just the older versions are replaced by newer ones (what could be a problem in case you really need to delete something).
If you have added your article and you are unable to find it, it is probable that you have selected another language while writing that the language of the article and thus the article was saved into a different language version. Try typing its name into the search box in the upper right-hand corner and click on "Search". The article probably appears and you will perhaps find out that it was saved as an article in Czech. There is a menu on the left side from the search box. Click there on "Move" and rename the article. If you are not able to move the article, contact the administrator.
If you are not able to find the article this way, check the list of all pages of this web. You can find there is the respective page does not exist under a different title (typo...).
If your page is not there, it was never saved. Make sure, you have really saved it (other browser opened?) and otherwise contact the administrator.