… something yellow and happy in a text message

SMILEYEMOJI

Think of a small, cheerful symbol often used to express joy in digital conversations.

This clue hints at a common text message symbol that's yellow and represents happiness. The answer is "SMILEYEMOJI," combining "smiley" (a happy face) and "emoji" (the digital symbols used in texts). The yellow color is a classic feature of the standard smiley face emoji, making it a straightforward but playful reference.