>>4 Hello, if someone posted your phone number then likely it has already dissapeared. Most of the pages on 4chan only last a short time as this site only keeps 10 active pages at a given time. (NOTE:THIS section "lounge" does not follow this rule as well as some others.)
Most likely your number was put in section /b/ OR Ramdon, if so there is no concern as the page would have dissappeared within hours of posting.
If you want to check this you can try searching the site using google (look under gogle ADVANCED search) but as google doesnt index this site completely most likely you will come up blank.
if you only got one text then dont worry.